It's pretty much as other people talked about, I used OpenCV to try to detect the board, and then isolate each tile, and then used Tesseract to try to figure out the letter. The biggest problem I had was whenever the red score bubble landed on a tile, it would fall on top of the latter and thus lose information so I ended up having to create training data and associating that to get the letter. I was able to get to about 98% accuracy and it was relatively robust until they created a new app that I haven't had time to adjust for.