Monitor if circuit is open or closed?
I don't know any part numbers off the top of my head but they do make Current Sense IC's which basically measure the voltage drop across a very low value (0.5 ohms or less) resistor.  You set the threshhold at one of the IC pins with a voltage divider and another pin gives you a TTL high or low output.  

We used these to monitor current levels in an RF amplifier system, but if the threshold value is set close to zero I suppose you can use it to monitor open/load conditions.