you could potentially tap into the door lock circuit, its electronic after all, find a positive that switches on with the door lock, and ground it, then wire that do a small speaker or horn, or a stock alarm "chirp" systemother than a full alarm installation thats my two cents.
JSCHERF92's 2005 Abyss Tein H.Tech SpringsBadge-less exterior w/tinted tails and 20% windowsSony/Alpine aftermarket sound systemRed LED interior/headlight/grill/underbody lights