I can't install it on my Nexus 7 tablet. Maybe because it expects a phone?

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.

Hey OP have you built any other FOSS versions of webapps?

You can find some more projects on GitHub [1] as well. But the only web apps are "Localize" [2] for translating Android applications and "Ballmanager" [3] which is an online soccer managing game.

[1] https://github.com/delight-im [2] https://github.com/delight-im/Localize [3] https://github.com/delight-im/Ballmanager

First of all, good job.

Secondly, do you have any plans to put the project to practical use? Or is it a research/tinkering project?

Thank you :) First and foremost, this has indeed been a tinkering project. But now, I think there may be enough potential to put this to a good use. Did you think of anything specific when you referred to "practical use"? Actually, the app is live on Google Play and this may already provide some practical help to users.