XBM to LCD by USB - displaying XBM images and videos on a Nokia LCD or cheap OLED sent via USB to an ATmega328
The Smack-'n-Go Reverse Kitchen Timer - smack it against a conductive metal surface and off it goes, thanks to magnets
Literary clock widget for Android, telling the time by quoting passages from literature that contain the current time
An Android app that looks around for specific Bluetooth beacons, and transfers your Spotify playback from one device to another as you are moving around in different places in your home
Tired of replacing batteries in your mouse, but not willing to give up the comforts of wireless data communication?
DTMF Music Box, GSM module on a Raspberry Pi playing "music" through DTMF tones whenever you call it
The 4 Chord USB MIDI keyboard. Play all those hit pop songs using the infamous four chord progression (I-V-vi-IV) with just a press of a few buttons.
A "smart" and utterly useless IoT power plug that tells you via Android app and tweets whether you plugged it in a power socket or not.
The "fitness tracker" Android app that counts the steps you're walking while roaming around like a maniac during phone calls.
Illuminating a wooden, DIY shot glass tray as mood light for a party, including a drinking game as easy and effective as Heads or Tails.
Integrate the Nokia 5110 LCD into own PCB designs and create display data and animations straight from XBM images.