I don't use that app so i dunno what do you mean by in the "same" room.
Even if you use GPS module it won't work indoor.
Edit: Which Emteria version do you use?
Is it below v0.61?
I tested the app, it doesn't work with microG.
It says there is no internet connection.
By the way, you can host a playlist on Ipad as you're doing and ask your customers to access it through the webpage which was created during setup.