Build a car hacking spy device to remotely read and send CAN commands and track GPS location. All based on open source software/hardware.
Amazon Alexa like device running on the Beaglebone.
We created a vi that can synthesizes different instrument sounds by generating different ADSR envelopes. Then deployed vi on the BeagleBone.
An alarm clock with a separate speaker forcing you to get out of bed to turn it off!