Id have to be dull and say the alarm i got in the 'two for fifteen quid' deal at the BMF. Doddle to wire up if a little tiresome removing fairing panels to hide the sensor and the siren. same features as many more expensive deals though. adjustable sensitivity of the vibration sensor, flashing indicators on triggering, self powered siren on hold-off relay so you can cut all the wires you like and it'll still deafen ya.
other than that i reckon secret designs i just bought for a personal electric vehicle freshly robbed from clive sinclairs secret norfolk labs.