Airbag for bikes
There are a lot of cool looking bike helmets out there but if you want something that doesn't look like a helmet but keeps your head safe in an accident consider the Hovding.
It's sort of an airbag for bikes; you wear it on your neck and if you happen to fall off your bike and your head is in danger, the airbag pops up and quickly (in a tenth of a second) covers your head against impact.
It uses combination of accelerometers and gyrometers to sense if you're just riding or in an accident.
If you don't like wearing helmets because it's hot consider the Hovding.