The GPS Scrambler was a GLA technology developed later in their war against the 'imperialist aggressors', and then handed out sparingly to generals who had attained a certain rank and wished to use it. The GPS Scrambler was a much-prized technology among GLA commanders since it effectively allowed them to hide a small group of any units (bar Angry Mobs) from enemy radar. Essentially, the units that the GPS Scrambler was applied to would become 'stealthed' units, invisible except to special enemy units adapted to detect stealthy foes. The tactical implications of such a power were immediately obvious, adding to the all-important surprise factor of the GLA's most successful attacks.
Prince Kassad introduced the GPS Scrambler to the GLA, and was able to access it at a far earlier stage - and more frequently - than his peers. Following his split from the GLA, he took the technology with him. Not wishing to lose such an advantage the new GLA supreme commander ordered one of his generals to attack Kassad and take the technology from him, which he duly did.
Cloaking Field (TW III)
GPS Scrambler was supposed to come in three levels. Each level you bought would increase the area of effect. There are selection pictures for all three levels. The GPS Scrambler that's in the game only uses the first picture, leaving the other two unused.
Playing against a GLA computer player. they are able to use GPS Scrambler every 1-2 minutes, rather than the normal 2:30 (3:00 for Kassad), which is obviously another advantage for the computer player.