I recently had a look at the App Store and tried to find a mother app that is even more suitable for me (Note: in short I didn’t found one).
The missing ApplePay support bothers me, but looking at how often I use my it clearly isn’t a deal breaker.
What I found were plenty of other applications that allowed to use the phone as POS systems. The technologies are different and I wonder if thought about integrating that as well?
I wouldn’t go the way that Square went and use the headphone jack for reading out any information (there are magnet strip, chip and NFC readers available). There is a nice presentation on why ( https://www.blackhat.com/docs/us-15/materials/us-15-Mellen-Mobile-Point-Of-Scam-Attacking-The-Square-Reader-wp.pdf ) beside the fact that more and more phones have their own special headphone jack system.
But if you look at other companies such as SumUp they have dedicated handheld devices that communicate via bluetooth.
I would imagine that would be an interesting thing for for business, but also for private customers. In Germany there are plenty of second hand so called “flea markets” and there it would be useful as well to have the option as seller to accept credit cards.