Probably just as good to get an alarm mate....

Toad do a perfectly good one for around £70 on ebay, bought one a while ago for my sierra and it was actually quite good, less annoying than my clifford!

Easy to fit, and with good introductions, basically splice into door switches, indicator feeds, and central locking feeds etc.

ended with remote door locking with a total closure output.

Also there are some very cheap remote locking/unlocking only sets but the range is very poor.

Good luck

Rob,