I'm on Android, and I use:
- Magic film ViewFinder by Roman Medvid (version for medium and large format cameras)
- Exposure Assistant for reciprocity failure
- Lab Timer, Massive Dev and The Unofficial HC 110 Helper for developing B&W films
- Golden Hour+ for the position of the sun (love this one!)
- Easy Measure because I can't for the life of me estimate distances
- Analog Memo for notes (recently downloaded, not tested yet)
- Light Meter
I also have the PhotoPills app on my phone but never use it.