For sometime now I've been working on a new 65C816 emulator that runs on a cheap ESP32 module. The code base is almost ready to release -- I just have to finish the monitor application (based on my SXB-Hacker) so you can upload code into the RAM for testing instead of having to rebuild the entire thing every time. I'm getting very close.
ESP32 modules cost less than £5 (direct from China via ebay) or a little more in online store (like Amazon). My current configuration provides 252K of RAM, and 260K of ROM in the emulated address space. The CPU executes at around 6MHz depending how much I/O you are doing. Currently I provide a virtual UART and 100Hz timer with interrupts. The code could be expanded to access the ESP's other peripherals (including the WiFi, Bluetooth, 2xSPI, more UARTs, I/O pins, etc.).
I suspect the emulation could be made faster but its good enough for now.
ESP32s can produce video and I have reserved some RAM for this purpose in the emulator. Ideally I'd like to generate 800x600 monochrome SVGA. If that proves impossible then something lower resolution and with colour is possible.
