There's a really old thread somewhere on iRex's forum sort of along these lines. I don't remember if it dates back to the iLiad days or if it was from the DR1000 (definitely pre-dates DR800), but someone was asking about a similar capability.
My vague memory is that internally there is a connector that you can enable to see the terminal output. This is what iRex used for their own development. I think (this is going way back, so my memory is fuzzy) they also mentioned that if someone had a specific need and goals in mind, they would be willing to work with them to help get it working. I don't know if that offer still stands, or if a similar connector even exists in the DR800, but you could try sending a PM to Matthijs and see if he can offer any suggestions.