GPS is already installed on airliners. GPS satellites are
not capable of two-way communications. They are not communication satellites. They just broadcast a one-way signal in the blind from space down to earth. Read post
#332 or this
explanation from Garmin.
Planes can already be tracked from destination to destination using signals emitted from the plane (ACARS, ADS-B). However, in the case of MH-370 the plane stopped transmitting data. Similarly, you would loose track of a commercial truck, if the driver shuts off the tracking system.
Now, just to add another layer of complexity, the plane was also transmitting an hourly ping. This short transmission is not typically used for locating an aircraft. However,
the technicians at Inmarsat, cleverly used these pings to estimate the plane's possible flight path.