The irony of all this is that I'm currently working on a system whereby a solo player can run through old pen-and-paper RPG modules - and a key component of the system is Threat.
Of course, in my instance, the player will know what his threat levels are. After all, you can't hide information from yourself. My system is a long way off, but I plan on using a card draw mechanic to acquire and remove Threat from the PCs.
Now, if only I can finish working out the "AI" behavior. I'm trying to find something simple enough that it can be done quickly by hand, yet complex enough to make the encounters interesting and engaging...
rushl