How much interest would there be in an ultrasonic altimeter for ultralights? I found a sensor with a 10 meter/30 foot range, self calibrating for temp/humidity. Should be useful at 60mph forward speed according to the vendor, down to zero. Environmentally sealed. I'm building/programming a prototype now. Features: Visual readout in feet or meters (daylight readable 2x16 OLED) Audio output to a 3.5mm stereo jack - plays a series of tones every (TBD) feet/inches, goes to a solid tone at 6 inches. Able to enable/disable the R/L channels independently. Offset - to allow you to account for the vertical distance from the mounting location down to the landing gear. Adjusting this offset does reduce the range by the same amount. Runs on 12V down to 3V input. Sensor is at 10hz, which means plenty fast. I'm going to do some ground testing (i.e. stick it on the top of a piece of pipe, move at a good clip down a dirt road, and have a passenger raise and lower it) then (since I don't have my ultralight done yet) find someone to flight test it for me. This unit will be a dash top - I will be able to build it into a instrument form factor if there is desire in the future. Package shouldn't be more than 3.35x1.75x3in total. Sensor will be mounted remotely.