There is no better way to learn electronics than building your own gadgets. There are already plenty of cool smart backpacks available for cyclists. The Arduibag is a backpack you can build yourself. This open source project involves building a backpack that displays an arrow to let drivers know in which direction you are turning. You can also display messages on it.
You are going to need a temperature sensor, RGB LED Matrix, battery, power switch, and a few other parts to get started. More information is available on Instructables.