Inexpensive lidar distance sensors have hit the market in the past few years, and now they are joined by 60 GHz radar. The A111 distance sensor from Acconeer uses a 60 GHz pulsed coherent radar to measure distances up to 2m with mm accuracy and an update rate of up to 1500 Hz. The device has the electronics and antennas integrated into the package, so you don't have to deal with 60GHz signals on your PCB (!). The part sells for around $12 in single-unit quantities, which seems reasonable for what you get. It uses an SPI interface, which is great, but the part comes in a decidedly non-hacker-friendly BGA package.
Although the details are yet to be worked out, I plan to make a hacker-friendly sensor module with this part, including power supply and I/O level translation (at least). I'll additionally create a software library for interfacing with it (initially targeting Arduino).
I just became aware of the this part today, and ordered some right after I saw it, so that's about all I know. Note that the datasheet is dated yesterday. Next step: come up with a quick prototype PCB so I can get some mileage on it before designing the final module.
Finally, I intend to experiment with PCB zone-plates to collimate the radar beam into a tighter pattern for finer sensing. Unlike traditional lenses, zone plates work by diffraction, and can be made with flat sections of material that blocks the beam. In this case, the proper pattern of concentric copper rings on a PCB should be able to collimate the 60 GHz beam.
Oh, yeah, as usual, I'm releasing all the design files and software under an MIT license.