This totally hasn't been known for months or anything: http://wiki.maemo.org/User:Jebba/DBUS#dbus-send-tick -Edit- Oh, and instead of using the "enable/disable" thing, the dbus-send-tick thing linked above simply makes one quick vibration - the same vibration that the system already uses for other 'tactile' responses to UI presses. So it'd just have to be [button press] [vibration tick] instead of [button press] [vibration on] [button press ends] [vibration off]
[button press] [vibration on] [button press ends] [vibration off]
[keyboard opened] [touch screen vibration on] [keyboard closed] [touch screen vibration off]