I've been working for the last year on a light, sound, and motion control board for costume props. It's called the Mighty Microcontroller.
I financed the development through Kickstater:
There were a few bumps along the way, and I ended up redesigning the board virtually from scratch to use a processor with more IO ports, more ram, and a second 16 bit timer, and there was also a hiccup involving how much power the voltage regulator would be able to supply, but in the end, the boards I had made worked on the first try! More or less. There was a small problem with the sound which necessitated a patch*, but other than that, no major issues.
Anyway, for the last two months I've had the boards in hand and I've been writing the code that drives them while also putting together a kit which is one of the rewards for the Kickstarter. This kit includes all the boards, switches, leds, and other things you need to make your very own Ghostbusters Proton Pack with lights and sound.
Here's a video with me demonstrating it in action:
The "strobe" is really a 3W LED bulb made for cars, and it's powered by a tiny switchable 12V boost regulator. The kit also features vibration, though that isn't shown. But for that I had custom vibration motors made,and they are driven by a "switch module" which is a logic level mosfet with a protection diode that can also be used for switching other high current and higher voltage devices. And the LED modules it uses feature TLC5947's, which are constant current drivers with a built in clock so I can update them only when I need to send new data, and no resistors are needed for the LEDs.
The boards are also tiny, being made to be as small as possible an using all surface mount components. Here's some pics of those:
(* Regarding the patch, the issue with that is I could not update the LEDs and DAC at the same time because they were on the same data bus, and that forced me to skip samples, which led to pops and clocks, which I tried to smooth over with clever noise reduction algorithms, but when they didn't work to my satisfaction, I hotwired the LEDs to the serial port so they would have their own data bus.)