Rapid prototyping circuits like Arduino are a great resource when it comes to testing a design without having to worry about the setup of the base to test the design on. The same applies to the devices to be attached to Arduino itself : most of the times the I/Os are potentiometers, pushbuttons, LEDs, displays, [...]

This is based on Arduino. Four displays show the time. At the time a modified relay strikes a fire extinguisher which provides a bell-like sound. It has to be a CO2 type : powder or liquid types do not work.
It looks a bit Al-Qaedian, so be careful as to where you display it.

Also, fire extinguishers [...]

I developed this infrared remote control decoder for Arduino on my Arduino-compatible STK500 evaluation board for Atmel’s AVRs.
The sketch is pretty much standard C code so porting to non-arduino dev systems is almost immediate.

I actually developed the code in C for a smaller ATtiny24 for a specific project underway thenI adapted it for Arduino and [...]