Is there a scanguage device for class 8 semi trucks?

Not currently... nobody makes an OBD reader compatible with the SAE J1939 interface... supposedly in the next year or two, OBDIII will be adopted and standardized all across... automobiles, heavy equipment, heavy duty trucks, etc. Then a simple OBD scanner will probably be available. Until then, it's going to require the compatible engine software (e.g., DDEC for Detroit, Insite for Cummins, Davie for PACCAR, etc.) and an interface box (such as Cummins' Inline or NexIQ).