Implement Hex Editor/RAM Watch mid-frame reads (from scanline, CRT-based consoles only, example: Game Boy) + sync Hex Editor/RAM Watch with Debugger

[getCursorsExe]

This allows you to look where the game writes a byte outside of V-Blank. Note that this would decrease peformance, so this should only work when Debugger (or Hex Editor) is open. This also matches BGB's behavior (unfortunately, this is not a rerecording emulator, so rerecording has to be a separate request on BGB)

[YoshiRulz]

This is just the mid-frame pausing feature, though I suppose that's not actually on here so ¯\_(ツ)_/¯

[getCursorsExe]

Single-step debugging actually does involve mid-frame pausing.

[CasualPokePlayer]

This can only work for cores that actually have midframe pausing in the first place. Which currently very little cores actually give this.

Also Game Boy can give this behavior by just using subframe input so that's a poor example here.

You are best off with lua scripts/APIHawk and using memory callbacks here, as those occur midframe.