lyonsden and I just completed a redesign of our Arduino Mega Pinball Signal shield(nicknamed the Pinduino). You can read about it in this other thread, but basically we are *starting* to take signals off the flasher circuit and do cool Arduino-based things with them.
We've built some functionality around controlling addressable LED strips, but we're hoping the modder/arduino community can find other cool uses for this... RGBs, Servos, Wifi, whatever.
https://pinside.com/pinball/forum/topic/update-arduino-shield-propin-pinhead
-Wes