Using available parts and a 3d printer, I went from idea stage (sketch above) to a working device in one day.
Printing and designing in 3d allows a designer to build a case and mechanical parts around whatever is available. For example, I used an ultracapacitor from a Coleman Ultracap Screwdriver. It was simple to design and print a hollow cylinder to accept the capacitor--this would have been a major challenge a year ago.
First I printed a cylinder, scavenged the capacitor and found an LED.
I used Autodesk 123d (free) to design the 3d parts. Files are available here:http://www.thingiverse.com/thing:31650