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]