Keylogger for android

I'm in the process of moving from qwerty to another layout on my computers, and most other layouts are focused on the use of the home row. I also keylog myself to find out what layout would work best for me, with my usage pattern. (And it's a great backup if the program you're writing in crashes.)

Now I want to do the same on android. Home row isn't really a thing when you're typing with your thumbs, so I thought I'd make a new layout designed for thumbs, rather than hands. Step one is to figure out what I normally write, so a keylogger would work great. Then I can build markov-chains, do benchmarks and everything would be great.

Is that available, or do I have to write my own keyboard app that just does that?