Check out these alarms on ebay. These are quality alarms that have microwave emiter capabilties. The microwave emiter is the part that puts out a sort of field around your vert so no can get very close with out setting it off or being warned.

eBay Motors: car alarm remote starter 3D graphic 2 way LCD pager (item 8021047052 end time Oct-04-06 00:45:35 PDT)

eBay Motors: 3 remotes car alarm 2 way LCD pager remote starter (item 8058932498 end time Oct-18-06 06:31:02 PDT)

eBay Motors: LCD 2 WAY PAGERS REMOTE ENGINE START CAR AUTO ALARM (item 270033055128 end time Oct-01-06 19:15:00 PDT)

 

i am using the audiovox prestige, and it works great! that last one looks cool