Sounds like a decent tool for an engineer on the run...but then again, you'd likely have a real calculator with you if you actually needed one (doesn't everyone use computer programs for calculations these days anyway?)...so it might only be good to help someone out a few times if they urgently need one and find themselves without one...which seems pretty rare to me.
For someone in school, it may be handy since people often find themselves without a calculator in class or at a library/friends whatever -- so it would make a nice backup.. However, it would obviously not be permitted on any exams.
So it seems like that's all it can ever be -- a backup that may help in some situations...which probably makes it worth the price if it's reasonably priced. If reviews here are positive, I may give it a shot.