An interesting new commit has been found in the Android code review Gerrit that could allow your phone to become a Bluetooth keyboard or mouse for your computer. There commit has two parts to it. The first enables the HID (Human Interface Device) Profile in the Bluetooth stack while the second adds Profile Proxy to the HID stack.
In theory, by enabling these features, your Android phone becomes another HID and allows it to perform functions of those devices. Any Bluetooth keyboard, mouse or trackpad that you connect to your computer or phone is a HID. This commit turns your phone into one.