Can sorta simulate the Activity Meter but it's annoying manually defining responses. It's also weird because the game disconnects regularly during communication and expects the device to reconnect. But if you do it too much it just infinitely loops the same requests.

Definitely would be better to emulate it. I think it runs on the same HW as the Pokewalker, so you could work off a pre-existing emulator. But the ROM for the thing just isn't available anywhere. Will probably pick one up some time since they're cheap and the method of dumping its ROM is easy.