Jake, obviously the technology exists for the gps trackers, but like everything else, it costs money. Nobody wants to pay for it, and with 40,000 flights around the globe per day, nobody wants to monitor them all.
We have two transponders, and then there is the 'skin paint' of large metal objects flying through the air, from ground based radar, ie. old school stuff that they say shows the flight turned around and headed back towards Malaysia.
The case could be made that there should be a third transponder which only operates once airborne, from an independent power source (internal battery) which cannot be turned off by the crew or anyone else, that may indeed be the result of this investigation.
How much would that cost compare to the search effort that has everything from satellites to submarines trying to find it? It could be as simple as a something that transmits a constant and simple stream of data by a radio signal. A bottom of the line 777 costs $261M so if it adds .5% to the cost? If you also start to consider the fact that there ~could be~ a (granted, slight) chance for survivors, finding them quickly could make a difference too.
