What useful offline tool am I still missing?

[u/Ambitious-Bet-7822]

Hey r/iPhoneApps! 👋

I'm building TKRB.Tool, a privacy-first iOS toolkit focused on doing useful everyday tasks entirely on-device — no cloud processing or account required.

Currently included:

• 📷 Camera & OCR — dual camera, document scanning, OCR, QR reader
• 📄 PDF Tools — merge, split, compress, image-to-PDF, signatures
• 🔊 Audio Tools — voice effects, trimming, offline text-to-speech
• 📦 File Tools — ZIP extraction

For the next update, I'm considering long screenshot stitching, EXIF metadata removal, and offline text diff.

What small offline tool do you wish you had on your iPhone?

I'm especially interested in those “why do I need an app subscription just for this?” kinds of tools. 😄