Buddi of UK is getting ready to release a new personal GPS locator that is miniaturized in size to make it easier to carry around with you. The specs are not released at this point but it probably is a GPS GSM tracking device that notifies a network at a pre-determined time interval.
You will have to spend an initial £300 on the GPS/GSM hardware and then pay £20 per month to get the service which will include 24/7 customer support as well as a website to pinpoint your loved ones on a map
buddi GPS locator coming out soon -- NaviGadget