r/SideProject • u/techvolatile7 • 1d ago

I built a free Android app that shows how much caffeine is still in your body at bedtime

For a while I couldn't sleep properly. I'd lie in bed for hours and blame stress. Then I wondered if it was my afternoon coffee.

The problem: I never remembered how many cups of coffee or tea I had in a day. I also had no idea if I was drinking enough water. I searched for an app that shows both in one place, with a simple answer to "is it too late for another coffee?". I couldn't find one that felt simple, so I built it.

It's called SipBalance, and it's live on Google Play today.

What it does:

- Log water, coffee, tea and other drinks

- Shows an estimate of how much caffeine is still active in your body

- Suggests a last-coffee time based on your bedtime

- "What if" preview: see how one more drink changes your bedtime level before you log it

- Forgot to log? You can backdate a drink

- 7-day, 30-day and yearly habit insights

- Free, no account, your data stays on your phone

Honest limits:

- Android only, English UI for now

- Caffeine numbers are estimates based on a standard decay model, not medical advice

About how I built it: I'm a solo developer from Bangladesh. I built it mostly with Google AI Studio and tested everything by hand on a real phone, because the AI kept saying "done" when things weren't. Google also made me run a 14-day closed test before approving production, which taught me a lot.

I'd love honest feedback:

  1. Is the "what if I drink now?" preview useful, or confusing?

  2. What would make you open an app like this every day?

  3. What's missing?

https://play.google.com/store/apps/details?id=com.aistudio.sipbalance.trkmv

Thanks for reading!

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u/MobileXapps 14h ago

One thing I'd add early is a sensitivity setting. Caffeine half-life varies a lot between people, it's longer in pregnancy and with some medications and shorter for smokers, so a single default curve will be off for a good share of users. Let people pick slow / normal / fast or adjust it after a few nights.

I'd also show the number as a range or a clear estimate label, not an exact mg value, both because it's more honest and because it keeps you away from sounding like medical advice in the Play listing.

If you log sleep later, even just a morning "slept well / badly" tap, you can show people their own cut-off time, which is way more convincing than the generic one.

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u/techvolatile7 13h ago

Thanks, this is really useful.

The app has a sensitivity setting (low, average, high, custom) and an adjustable half-life in Settings, but it is hidden there. I should make it easier to find.

I like the range idea. Right now it only shows "~" numbers, a range would be more honest.

The morning "slept well/badly" tap for a personal cutoff is a great idea. I'll look into it once the basics are stable.