This sounds similar to actually an old-school trick/option for alarms. Its called passive arming. Don't know if it'll work, but turn off the ignition, remove your keys (take them w/ you). and close the door. Don't lock or arm the alarm. After a set period of time, the doors should automatically lock and supposedly arm the system. If it doesn't do it, than Toyota still has a crappy alarm system.
pretty handy, though if you forget to set your alarm or lock your doors.