Wow, I probably played with this for a solid 20 minutes. I always felt PinMAME's switch matrix input lacked the ability to really influence game events because there was no way to keep switches pressed down (to lock a ball, for example). This makes it easy! It works for me in Chromium (based on Chrome) but the sound does not work. The emulator doesn't work at all in Internet Explorer. I haven't tested any other browsers.
This is fantastic, for people who want to rip or record DMD animations this is absolutely perfect to trigger specific events!