I'm going to show you how to create a turn indicator for bicyclists that lights up automatically when you extend your arm to indicate a turn.
It's based on a small commercially available EL panel, to which we'll add a simple tilt switch and a band so it can be worn on an arm. If you prefer you could alternatively sew it into clothing or attach it to clothing with velcro.
This can be built either as a beginner-level project without soldering or as a medium-level project with soldering. This instructable describes the no-solder version that is really just a proof of concept prototype. Soldering will make for a more robust unit and it'll be brighter because there will be less resistance in the circuit.
armband (reflective LED bands are good but plain cloth would work just as well) (X 2)
tinfoil (aka silver paper)
plastic drinking straw
insulating tape (or regular tape)
I used these particular parts because they were what I happened to have available. Once you see the general principle of this build, you'll know what you can substitute from your own collection of bits and pieces...