Just started the app and its already usable. It doesn't have many features yet, though. For now, you can add up to 100 Bitcoin addresses (no xpub/ypub yet) and see their balance. You will just need a Blockonomics API key (free).

However, I forgot to ask what is your phone OS. I have both a Play Store and Apple Store developer account, but building iOS apps without an MacOS device is very difficult (I'm using Ubuntu), so putting it on the Play Store should be way more easy.