Raspberry PI configured as portable Software Defined Radio system.
Interfacing micro computers with real world applications. Using the PI as UHF remote digital radio receiver.
Reliability and endurance testing 24/7.
Comparative testing between two different types.
Tuning the hardware for testing.
Main controller unit.
Also check out the ATTiny Morse Code callsign generator. It uses an eight pin Amitel low power AVR. It is so small it can be built into a microphone if required.