AI Product · Case Study
Clinically-grounded AI for the parents of twins.
Most baby apps assume one child. Tandem is built from the ground up for two — coordinating both babies into a single sleep schedule and answering parents' questions from a base of published pediatric research, not guesswork.
Built by a market researcher and AI engineer to solve a problem in his own home — as the father of twins himself.
A short walkthrough of Tandem building a coordinated schedule for two babies and answering a parent's question with cited research — the live product, not a mockup.
Product walkthrough — video coming soon
Parenting twins is not parenting one baby twice. Two wake windows drift out of sync, two developmental clocks tick at different rates, and a tired parent has to reconcile them in real time. Tandem turns that coordination problem into software.
A joint scheduler optimizes both children's wake windows into one household schedule — naps, bridge naps, and bedtime — so parents aren't whipsawed between two conflicting timetables.
A chat assistant answers questions from a curated corpus of pediatric sleep guidelines and clinical literature — using retrieval-augmented generation so responses stay tied to real sources instead of generic AI output.
The model learns each child's evolving rhythm and adjusts to developmental phase — and, for preterm twins, to corrected age. One twin's data never contaminates the other's.
Sleep, feeds, and diapers log in a tap and roll up into trends — the data that powers the predictions, captured without adding work to an already exhausting day.
Parents act on this advice at 3 a.m. A hallucination here isn't a typo — it's a safety risk. So Tandem is built the way a researcher builds an experiment: to be measured, grounded, and verifiable.
Every answer is retrieved from and constrained to a clinical evidence base. Measured hallucination rate fell from 14% to 2.5%.
A three-tier eval harness — deterministic metrics, claim-level analysis, and human review — scores quality on every change, so improvements are proven, not assumed.
A hard architectural rule guarantees one child's data can never leak into the other's predictions or answers — the integrity guarantee a twins product lives or dies on.
Medical-keyword questions bypass the usual time-weighting and route conservatively, so urgent topics never get diluted by routine logging noise.
Production stack · Python · FastAPI · React PWA · Retrieval-augmented generation · vector search + reranking · built with modern AI tooling.
Tandem starts where the pain is most acute — parents of twins — a focused, well-bounded niche with no incumbent built for it. The sizing below is deliberately conservative and US-only: every population figure is drawn from CDC and peer-reviewed sources, and the revenue model uses a modest blended subscription assumption. The broader infant market is the expansion story, not the headline.
| Layer | Who it counts | Math | Size |
|---|---|---|---|
| TAMTotal addressable | All US households raising twins, ages 0–5 | 327,000 × $150 | ~$49M/yr |
| SAMServiceable available | US twin households in the core 0–3 sleep window, smartphone-owning | 208,000 × $150 | ~$31M/yr |
| SOMServiceable obtainable | Realistic 3–5 year capture, ~5% of SAM (range 3–7%) | ~10,400 × $150 | ~$1.6MARR |
SOM range: $0.9M–$2.2M ARR at 3–7% penetration. For reference, the leading generalist baby-sleep app (Huckleberry, single-child) is estimated at ~$7M ARR — so a focused twins product reaching one to two million in recurring revenue is a conservative, well-supported target, not a stretch.
No incumbent is built for two-baby households. Huckleberry, Napper, and Nanit are all architected around a single child — "add a second baby" means toggling between two profiles with no coordinated wake-window math and no joint bedtime. The only dedicated twins app on the market is a community log-book with no sleep intelligence at all. The offline alternative — a human sleep consultant experienced with multiples — runs $795–$1,915 for a single engagement, and many charge twin families a premium on top. Tandem sits in the open space between a generic single-baby app and a one-time four-figure consultation.
A premium consumer subscription. The market model above assumes a blended $150/yr ARPU — positioned between leading single-baby sleep apps (~$120/yr) and the one-time cost of a human consultant, and far below it. Twin families are a documented high-spend, high-intent cohort, which supports both a premium price band and stronger willingness to pay than the generalist market.
Twins are the beachhead, not the ceiling. The coordination engine generalizes to any number of children, and the clinical foundation applies to every infant — so the same product extends naturally into the far larger single-baby market once the twins niche is owned. That broader market is upside; it is deliberately not counted in the figures above.
Population counts are sourced facts; household-stock, ARPU, and penetration are clearly-labeled estimates. Full citations in the Sources section below.
"We know your babies — not just babies." Tandem is the only system built for the chaos of raising two, not a single-baby app with a twin toggle bolted on. The brand meets parents in the mess and walks them to clarity — grounded in evidence, and never precious about it.
tandem.
"The Clasp" — two crescents, backs together, meeting at a single gold point. The dot is the bond between siblings: "I've got your back."
The two children's colors sit a deliberate 50° apart in hue — so a sleep-deprived parent tells them apart by color, not just position. Gold carries the palette's entire warmth: one warm note against two cool ones.
DM Sans — one humanist family at multiple weights, lowercase throughout. The wordmark closes on a gold period. The brand doesn't shout.
"The friend with twins, tattoos, and a stack of research papers — the one you call at 3 a.m." Direct, honest, warm-not-soft: irreverent enough to swear in marketing, disciplined enough never to swear in clinical guidance.
Not a medical device. Not a generic tracker with a twin toggle. Not soft or precious.
A working production system — clinical corpus, joint scheduler, evaluation harness, and a React app — in daily use in its creator's own home.
Hardening for multiple households and preparing the twins experience for a broader release.
Extending the coordination engine and clinical foundation from twins into the far larger single-baby market.
Tandem isn't a slide — it's a shipped system. Here's the research, analytics, and product toolkit it puts to work, mapped to exactly where each one shows up.
Tandem exercises the production, AI, and market-analysis side of the toolkit. The statistical-research side — survey design & programming (Qualtrics), in-depth qualitative interviewing, regression / GLM, causal inference, and conjoint / MaxDiff in SPSS and R — is documented across 10+ peer-reviewed publications and seven years of applied SMB and nonprofit studies. See the research →
Market figures are built from primary and peer-reviewed sources. The population counts are hard demographic facts; the revenue assumptions are stated and conservative.
Derived figures (household stock, ARPU, obtainable share) are the author's own estimates, clearly labeled as such, built on the sourced inputs above.
Happy to walk through the product, the architecture, or the underlying research.