Where should the photos actually be stored?

In the app sandbox on the device by default, not the camera roll and not a server. Writing to the camera roll drops private photos into whatever backs it up, and a server means you are now custodian of sensitive images. Offer cloud backup as an explicit opt-in and say plainly what it does.

Is the ghost overlay hard to build?

No — it is an absolutely positioned Image over the camera preview at low opacity with pointerEvents none. It takes minutes to build and it is the difference between a usable comparison and a folder of unaligned photos, which is why it belongs in the first version rather than a later one.

How to Build a Progress Photo App with AI (2026)

What a progress photo app needs

Camera with a ghost overlay of the last photo for consistent framing
Dated timeline grouped by month
Side-by-side compare of any two dates
Multiple tracks — front, side, or one per project
Photos stored on device, not uploaded anywhere by default

The screens

Screen	What it does
Timeline	Photos by month with a track selector at the top
Capture	Camera with previous photo ghosted at low opacity and a grid guide
Compare	Pick two dates, view side by side or with a drag slider
Photo Detail	Full-size photo with date, note, and optional measurement
Settings	Tracks, reminder schedule, passcode lock, export

The data model

Track: name, poseHint, createdAt
Photo: trackId, fileUri, takenAt, note, weightKg (optional), bodyFatPct (optional)
Reminder: trackId, weekday, timeOfDay, enabled
Settings: passcodeEnabled, defaultTrackId

The build prompt (copy this)

Paste this into ShipNative and it becomes a working React Native app with these screens, navigable in a live preview, in about two minutes:

“A progress photo app. The capture screen shows the camera with the most recent photo from the same track ghosted on top at about 25 percent opacity plus a rule-of-thirds grid, so the new shot lines up with the old one — this alignment overlay is the core feature and everything else supports it. Photos belong to a track (front, side, back, or a named project) and are saved to app storage on the device with a taken-at date; nothing is uploaded to a server unless the user explicitly exports. The timeline groups thumbnails by month with a track selector at the top. Compare lets the user pick any two dates and view them side by side or with a draggable divider over a single frame. Photo detail shows the full image with an optional note and optional numeric fields for weight and body fat. Settings holds tracks, a weekly reminder that fires at a chosen time, an optional passcode lock on app open, and an export that writes the selected range out as a shareable set. Works offline. Screens: Timeline, Capture, Compare, Photo Detail, Settings.”

Then iterate with small, screen-specific prompts (“make the primary button bigger”, “add an empty state”), preview on your own phone, and export the full Expo project whenever you want. The full method: how to build an app with AI.

How it makes money

Subscription ($3-5/mo) for unlimited tracks, compare, and cloud backup, with a genuinely useful free tier of one track. Be careful with the category: this app holds photos people would be upset to leak, so on-device-by-default storage and a visible privacy stance is a selling point rather than a compliance chore.

Implementation and the revenue math for every model: how to make money from an app. When you’re ready to ship: App Store and Google Play publishing guides.

Build it now

The prompt above is free to run at shipnative.dev — working progress photo app on your phone today, full code export, no credit card.

How to Build a Progress Photo App with AI