Simul on smartphones?
The only problem being is that it would be hard to track cheating. In person events are more suitable for this. Although concepts are nice to consider. Albeit chess.com has anti cheat software, the temptation someone would likely cheat is inevitably higher due to publicity.
#4 explained why its not gonna happen. Great idea, but cheaters woild ruin everything and we can't rely on good will of people and think they won't cheat.