The Nest might work with your 2 wire system. Call Nest and describe your equipment. They may be able to guide you.

The other approach is to install a ground connection which is the C wire. Look for the 24 V transformer connected to the furnace. One side is the red wire, the other side can be used for the C connection.

Marc Well, you are one spamming machine! Congratulations!

We just put in a Nest with a 2 wire setup. Works like a charm with only the two wires.