Thanks! Yeah, the app draws a line between the points. This isn't noticable if you're drawing slower (or if the device is fast enough), but if you're driving faster than it can be processed, the lines do show. I'll try to see how to improve on that, the plan is for the app to be useful on Android phones and iPhones as well.
Even in Photoshop, if you draw a very quick curve, you can see individual vertices along it. But Photoshop seems to quickly interpolate curves instead of straight lines, so you get a rough approximation of the curve you're drawing between the vertices. It's pretty good for hiding how it works.