Key remapping

Reference example: https://github.com/Clam-/TraditionalT9/blob/master/keymap.txt.sample

Use an app that reports keycodes and map the original keycodes to the keycode of the key you wish to remap the original key to.

Place keymap.txt on the SD card in the location where backups are also stored. (Should be SDcard/traditionalt9/ but you can double check by using Settings to "Backup dictionary." Where the backup is stored is where the keymap file will be read from.)

http://developer.android.com/reference/android/view/KeyEvent.html
May be useful for reference.

By default remapping will only happen when text input is active. You can turn on the setting named "Translate keys" to have the remapping happen always.