This is something we will be seeing more and more; LED lights incorporated everywhere. Helmets, leathers, even boots. Now we get to see them integrated into a backpack. French Bagster has one called the Starlight, here is what it has:
The Bagster Starlight is a 30 liter backpack, with soft foam straps and in the back, two red LED strips that receive a signal from your motorcycle's stop lights. In essence, you place a small radio transmitter between the light bulb and the housing, and when you hit the brakes, it sends a signal to the backpack which then lights up the LEDs.
It's interesting to have a stop light at the height of a backpack, since that is more or less the height of the eyes of car drivers. So they can see more quickly when you hit the brakes. Trucks have an even more difficult time to see your brakes, so this could help them.
The backpack itself uses 4 x 1.5 V batteries to power the LED lights. On its own, although you can use rechargeable batteries, you will need to take them out to recharge them every time. IMHO, I think they should have had a USB charger with it.
For the rest, the baggage comes with a rain cover (that will not obscure the stop lights...), a special pocket for the rain cover and two pockets with zippers.
The whole thing weight 1.5 kgs. Cost will be around €150. The thing just for released, so it'll be a while before it hits stores on the web.