Radar jammer
From Halopedia, the Halo wiki
The Radar Jammer is an equipment item that scrambles nearby players' motion sensors and HUDs when deployed. While it can create chaos for enemies, it has the same effect on teammates, be careful!
References were found to it in the Halo 3 Beta code[1] and its effect was seen in leaked beta footage. It has now been confirmed in the June issue of GamePro.
Sources
{Equipment List}
