This is a real cool project if you are also into biking (or perhaps skateboarding or inline skating). You can wow your fellow bikers with this stuff and even drivers behind you! And again, this is something that you can finish doing in a weekend, given the right tools. In this project, you basically develop your own blinkers. It needs an Arduino (or similar) kit and some LED light bulbs. Once you make and program them, you can put them on your jacket to make it a “wearable” gadget, or attach them to your bike, or any other vehicle, for fun.
CHeck out the video here that shows how to do this.
In addition to Arduino, it also uses conductive threading and sewable electronics. You will also need to be (or get) familiar with sewing.
You can get some detail instructions from https://www.instructables.com/id/turn-signal-biking-jacket/
You can purchase the Arduino kits from the site, or from Techblueprint.net. There is a promo for the Starter Kits available for $1 (plus shipping) there. You can also get the more Upgraded Advanced Kits with CD Tutorial, with many more items including LEDs, on sale for $54.99. You can also get a free sensor with that kit by entering FSATK code at the time of checkout. The best deal may be getting both the Starter and the Advanced Kit along with the Free Sensor.