[ingenium]

The company Zeo made a product that did this (Zeo Mobile). It was a headband with 3 sensors on it, and it connected to your phone via bluetooth. It works great. Unfortunately they recently went out of business and took their site down, but you can probably still find them on eBay.

[rdl]

The sad thing is the dry electrodes are considered expendable. They're no longer available. It does look like some people have been able to replace the pads and headband using fabric, though.