Mark is writing the plug in for Homeseer. You can find the latest here:
I believe you can use the external script for the I/O units but that may also be something Mark has on his list. Insteon is tough to support because each new product has to be coded separately. For 18 month HS decided they couldn’t support a dedicated person to it as HS is trying to support many different interfaces and they couldn’t dedicate a full person just to Insteon. Mark has picked up the ball but I don’t know if he is compensated by HS or not.