In theory, one possible outcome of "the singularity" will allow people to transfer their consciousness into a machine. A machine, then, that could significantly alter their perception of the "world", simulating the world individually for each human. Undo would simply rewind the simulation, and change the user's memory of the events as needed so humans could fully interact, and any one could rewind short things.
Would probably need to have limits built in, otherwise the world would be in a constant state of rewind.
For instance, tiny, localized rewind effects have low to no cost - oops, dropped my phone and it broke, let's go back a few seconds. No need to rewind the day for anyone else, and the user would just have to accept the "lost" time since the rest of the world kept going on.
Large area rewinds (The rainstorm caused too much damage), or rewinds that affect a lot of people (sports exhibition), or rewinds that pass through a lot of time (I wish I hadn't entered into this relationship) would require greater resources, such as "lifespan", or would have to require several people wanting the same exact rewind, etc.
Then there are human factors. "I wish I hadn't gotten married and had 2 kids" - what happens to the kids if this rewind is successful? "I wish I had killed modern-day-hitler when I had the chance"
These problems would be present in any undo system - not just a simulated human system.
But as far as a reasonably possible future, many of our time believe the "singularity" is inevitable.