The guys above are spot-on - immobilisers are really good at stopping someone hot-wiring your bike's ignition, something that just happens all the time, right? Yeah, right!
What differentiates alarm systems is really the passive current draw - particularly if you don't ride very day. For example, my daughter's SV has a Datatool system that flattens the battery in five or six days unless she regularly runs the bike up for half-an-hour. When the battery goes flat, the alarm goes off - it thinks someone is disconnecting the battery.
Contact Meta (
www.metasystem.co.uk) - unless they've radically changed (in the last two weeks), their systems are good, they're reliable and have low current draw, and they don't sell their stuff to cowboy fitters either.