Detexify is a LaTeX symbol recognizer for Android-powered mobile phones. Think of it as an interactive LaTeX cheat sheet. Draw a symbol into the clean interface and it'll return a list with the most similar symbols and details for each one.
It uses server-based machine learning.
It's freely available on the Android Market, you can have a look here: Cyrket link
Or use the 2D barcode on the right with your Android barcode-scanner app.
There is a version for PC and Mac browsers here.