It's a feature built into the ROM. OMNI ROM is the only one I can think of with it, maybe paranoid android too.

Sent From Burning Gundam
Main: LG G2 D-800 {Tmobile)
LG Opt G (e970)
Hybrid radios for E970
Surface RT 32GB--Kindle Fire 1G_CM11--SGS Vibrant_CM11
Owned: G1(Backup)-> Mytouch3GS(Sold) -> SideKick4G(Traded) -> MyTouch4G(Sold) -> Sensation 4G(Sold) -> Galaxy Player 5"(Sold) ->Nexus 4(broken)->LG Opt G