I wanted to do MotoVlogging, that is talking while riding a motorcycle.
Problem is there is a lot of noise, like wind noise or the engine sound (even thought my Honda isnt very loud).
At first I just tried my smartphone-headset, even tried it with some foam around the microphone, but the results were still unusuble.
Than I tried a small computer headphone, the outcome was better but still not good.
After that I decided to just make life easier for me, went to my local motorcycle-stuff store and bought an motorcycle-headset. Result: unbearable!

Now what should I do? I dont want to get some 200€ microphone...

A friend told me there are microphones they use in theater that will just record whats right infront of them. So you position them to your mouth and engine sounds wont bother the mic?

 

Your friend could be talking about the Coles Lipmic, used by sports commentators, but that's too big to put inside a helmet (and 2 times 200,-)
Other than that, it's quite a challenge to record any decent audio in that situation. You certainly need to cleanup & process the recording afterwards.

What are you recording on? If on a Go Pro, you won't have Phantom power, that's what most lapel-mics use. You'd need a phantom adapter on batteries for them.

So then you could look at a dynamic lapel mic. They don't need external power, also are less sensitive (which is good, because you wanna get rid of as much bike-sound as possible).
I know of 2 dynamic lapels (Lavs), Shure SM11 & Electro Voice 649B, but they're not that small, and still.. a normal mic needs air to record sound, and that's not really available inside a helmet..

Another option: Why not record a scratch track on your phone with some mic you have, and afterwards record it again, and process it to recreate that 'onboard sound'? When riding, you could focus on recording the bike sound, which is another challenge..

http://www.canford.co.uk/Products/92-392_COLES-4104-MICROPHONE-Lip
http://www.shure.com/americas/products/microphones/sm/sm11-lavalier-microphone