you could use something like this
http://www.ebay.com/itm/Car-Remote-Control-Central-Door-Lock-Kit-Locking-Keyless-Entry-System-B98B-/231043575887?pt=AU_Car_Parts_Accessories&hash=item35cb45304f&vxp=mtr
,also u would need latching relay and 12v dc-regulator to power it ,
or this...