While I'm a huge fan of stylus input and may pick up a pogo to play with, the tip of those things is huge. It looks like it would be like trying to sign your name on one of those 90s-era signature pads that the UPS guys carry around. It might be fun for sketching and screwing around, but unless they come up with a tip that's actually shaped like a pen, it looks like a nightmare for trying to *write* with.
Still--it's your twelve bucks, maybe someone will have a better answer about the app.