Gens+ REWiND! is an Emulator with added support for real-time rewinding! Feel free to call this feature "sands of time" if you want ;)

gGens (MD) is described as 'Free, ad-driven emulator for Android that emulates the classic Sega Genesd Sega Mega Drive videogame systems' and is a Game Emulator in the gaming software category. There are more than 25 alternatives to gGens (MD) for a variety of platforms, including Windows, Linux, Mac, Android and Xbox apps. The best gGens (MD) alternative is RetroArch, which is both free and Open Source. Other great apps like gGens (MD) are Kega Fusion, RetroX, RetriX and Nostlan.
Gens+ REWiND! is an Emulator with added support for real-time rewinding! Feel free to call this feature "sands of time" if you want ;)

Gens Re-Recording, formerly known as Gens Movie Test, is a modification of the highly popular Gens emulator by Stéphane Dallongeville (also known as Stef). This modification includes slowdown, recording and playback of controller input logs, dumping of AVI files, and Lua...
"jEnesis" is a Sega MegaDrive/Genesis Emulator entirely written in Java.
Features
Everything written completely from scratch Custom Java Motorola 68000 CPU core VDP emulation with all DMA modes Horizontal & Vertical Interrupts Support for PAL.