I find the website works perfectly fine through the mobile browser, though admittedly I haven't tried to write a post from my phone. There actually is some mobile apps, which I haven't tried in a few years. The used to kinda not work all that well, but it was nice to receive push notifications. There is a good chance they've been improved since I last tried any of them.
Here is the page of all the apps on Hive.
https://hive.io/eco/
I've heard good things about the Ecency app, but i wanted to try it out before i started suggesting it to everyone. Maybe when i get the time i'll try them all out and see which is best, make a little video about it for everyone.