Thing about cricket though is unlike other games you appeal, for a catch, for a stumping, for LBW and somebody has to make a judgement. So shouldn't you be able to counter appeal the appeal if you feel you're not out? Another thought occurs, if there's no appeal can the umpire give someone out caught behind, stumped or LBW?
Technically - no. There was an example in the last game where no-one appealed but it appeared from the evidence that the player was, in fact, out. A caught behind I think.
Hotspot is a disaster due to the thin edges not registering in some cases - snicko is better but the technology used to generate a valid sound wave after removing extraneous noise takes far too long.
Hawkeye is also a problem in terms of the ones that "just clip" the stumps. However if asked whether whether it or an umpire was best placed to predict the path of a ball after contact with the pads I would go with Hawkeye.
It would be interesting to try out an "umpire only review" - although I do fear that you would end up with them referring everything. The latest I heard was that the ICC would introduce their own fully independent system where the 3rd umpire sits in a van like in RL and has control over which replays he sees. However we know from experience this will never eradicate human error, as witnessed at "Manchester Magic".