Yatse is my Kodi (formerly XBMC) remote Android app of choice.
The Yatse Remote app allows me to control the media center from my phone. It’s so good doing that, that ever since I installed it, I never needed to pull out the HTPC keyboard / mouse!
There are plenty of alternative Kodi remote apps, including an official one from the XBMC team. I briefly used the official app a while ago (maybe early 2013?), and got quickly frustrated.
The Yatse app is free, with a $6.99 unlocker for extra features (and developer support). I never had any need for the extra features, so I purchased the upgrade only to support the developer.
Yatse also has various plugins for even more features!
App Highlights is a recurring series. From time to time, I highlight one Android app that I found useful. Feel free to suggest apps for me to highlight, but be advised that I focus on apps that I actually use.