[ferdterguson]

Not sure if you are aware of detexify [0], but it recognizes my trackpad-scratch quite well. The backend and all of the training data are open source, so you could indeed implement this yourself if you wanted.

I'd buy mobile app any LaTeX OCR software.

[0] http://detexify.kirelabs.org

[aqsalose]

Yes, detexify is amazing! That's probablly how I got the idea in the first place... "Imagine if detexify would automatically read all of my math writing, not symbol by symbol what I draw with mouse."