Reddit reviews Bicycle Bike Turn Signal Brake Light Horn

Here's a list of links to the parts I used:
Engine kit: http://www.bikeberry.com/gas-engine-kits/49cc-flying-horse-5g-pull-start-bicycle-engine-kit-4-stroke.html

Muffler: http://www.bikeberry.com/engine-kit-parts/performance/phantom-bikes-4-stroke-extended-exhaust-muffler-pipe.html

Custom Rear Sprocket adapter: http://www.piratecycles1.com/picycbspad.html

Upgraded Throttle: http://www.sickbikeparts.com/catalog/product_info.php?cPath=25&products_id=156&osCsid=ro97nt679htq0m6id3ie584815

Forks: http://www.beachbikeoutlet.com/shop/nirve-springer-brake-pivots

Seat: http://www.motostrano.com/Felt-Hotwheels-Cruiser-Seat-p/950603.htm

Rear Brakelights/turn signals: http://www.amazon.com/Bicycle-Bike-Signal-Brake-Light/dp/B006BQEDEQ

I custom made the rear rack, the speedometer/killswitch enclosure, and faux oil box, Customized the fenders and made a license plate. The Headlight has been gutted and replaced with brighter LED lights.

And the single review says it stops working pretty quickly.

Get one of these instead. $6 and it has turn signals as well as the same type of brake light shown.

Good news! Something like that already exists: http://www.amazon.ca/Bicycle-Bike-Signal-Brake-Light/dp/B006BQEDEQ

As I said in the post, we believe hand signals are the safest option for signalling because they are most recognized by drivers, are required by-law in most places, and are more visible to very close vehicles than low-mounted lights. We want to make hand signals more visible at night.

You raise an interesting point though- that even an automatic hand signal-activated system should be able to be activated manually for those situations where it is unsafe to remove your hands from the bars (even though the law may disagree).