i used the proxy ytrick to install this on my 520. It works perfectly fine.
I would imagine the quality is low because it is coming from a video feed or something similar, rather than taking a lot of high-resolution shots per second.
As for this only doing 2 shots, I set up 3 items at different distances and it let me select all 3 as the focal point (with the associated depth of field changing). The contrast of these objects needs to be low though for it to work effectively. If it captures frames for the entire focus range, it may be possible for them to implement a focus adjustment at some point.
Definitely an interesting app, despite being rough around the edges!