Not sure if this counts, as these are SoC, but still very high difficulty and very cool:
‘So you think you’re pretty good at soldering really tiny parts onto a PCB? You’re probably not as good as [Shibata] who made a GPS/GLONASS and Geiger counter mashup deadbug-style with tiny 0402-sized parts.
‘The device uses an extremely small GPS/GLONASS receiver, an AVR ATxmega128D3 microcontroller, a standard Nokia phone display and an interesting Geiger tube with a mica window to track its location and the current level of radiation.‘
That sounds like a challenge... given that someone has already done something similar with a GPS receiver:
http://lea.hamradio.si/~s53mv/navsats/theory.html