1) Useful.
2) Safe.
That'll be cool. As for what this guy's actually contributing... Not really sure.
(Other projects on their site also kind of sound like bullshit. For example:
"The idea is to stimulate your brain with direct current (in the case of tDCS) or with square waves of current (in the case of CES) which can either raise or lower the potential energy of the stimulated neurons, depending on the orientation of electrodes. This allows them to fire more or less easily, and activates or deactivates a given region, thus engaging certain brain states." -http://www.grindhousewetware.com/thinkingcap.html
Sounds like either pseudo-science or wishful thinking to me.)