There is one called CPUVue from the "Shack". It will monitor your system and CPU. I believe it is only available online, though. If you can find one, there is always "DigitalDoc", which not only will monitor temps, but also control fans.
Enermax makes a drive-bay mounted device with 2 digital displays and two thermal probes (thin, not bulb type). It retails for about $20.00 and www.virtualhideout.net has a review of it. Terry at www.warpfactor-e.com is considering carrying it, you might want to give him a ring.