Exactly. Sorry, should have mentioned that. I wasn't really sure how to handle this. The problem is that (a) the app is optimized for phones and (b) it has to ask the user to enter their phone number manually if the device has no telephony features and (c) it can run on a single device only. I wanted to prevent users from the confusion that arises when they have the app on their phone already, install it on their tablet as well and then see that it stops working on the phone.