We started writing a simple math editor, then we realized that writing math symbols was boring on Android. We also realized that writing a system keyboard for Android could make us happy, because all the existing ones was not so useful, so we did it. With a pretty system keyboard, we realized that the remaining steps in order to have a fully functional Bluetooth keyboard was not so many. So, here is Zeta Math

Zeta Math will allows you to write some math documents offline on your android phone, you can use its keyboard as your default keyboard and switch it very quickly as you want with a simple shortcut (⌘+K).