SeattleKCD

What's the possibility of getting a radar altimeter part? Something that is in the tech tree, uses power, and will give you a read out of distance to actual surface (not mean surface) when you are say under 10-5K meters. I hate it when a lander mission fails because I can't tell how far up I am and I misjudge and decelerate too late. My kludge solution is to carry a throw away jettison-able part that I detach around 5-10km off the ground. I watch it fall and note it's distance when it impacts.