TFR - Terrain Following Autopilot. There is some?

There is some gauge / Autopilot that allows to very low flyig - following terrain? You know, up and down the hills... I know many modern figters / bomber have TFR to evade enemy radars...
Many FS models have the radio altimeter that basicaly indicate the heigh over the terrain... so I think is posible, to keep a constant heigh like the ALT autopilot but link to the Radio Altimeter.
Ah, for FS2004 please..
Many FS models have the radio altimeter that basicaly indicate the heigh over the terrain... so I think is posible, to keep a constant heigh like the ALT autopilot but link to the Radio Altimeter.
Ah, for FS2004 please..