Connection between two Arduino

Hi,
I was looking at some electronic wristbands and I saw:
http://www.taptap.me

Basically they give you two of them that are connected and let you send a vibration (for example) to the other owner.
What kind of communication do they use? Do they have a sort of Sim card? Would it be possible to make a similar product with Arduino (I was thinking about Arduino Gemma)???

Thanks

Quote from the second link

HEY comes as a set: two bracelets that are linked to each other via Bluetooth and an app on your smartphone.

I suspect it should be possible to implement something like that using Arduinos and bluetooth modules. Are you sufficiently experienced to write the necessary smartphone program?

...R

Thanks Robin2,

At the moment I'm not, I've just started
studying Java for Android apps and I hope I'll be able soon...

So the bracelet is connected to the phone and the phone to the other phone-bracelet?
Seems not to hard to program