Thermometer problem/recommendation

Howdy.
Made a rye brown ale last night.
Or attempted too anyway. At this point, I have no idea what I'm going to end up with.
Temperature readings from my digital thermometer were all over the map.
Even with vigorous stirring, I was getting wildly different readings during the mash (bouncing around from 140F to 158F). Even just heating up the water, I was aiming for 166F (wanted to mash a bit high at 154F) and have no idea what temp I actually doughed in at since it was bouncing between 160F and 180F.
I can't imagine I was dealing with hot and cool pockets in the water because it was off the burner at that point and I was stirring it constantly during/between readings.
Not to mention this was only about 2-2.5 gallons of water as I make 2.5 gallon BIAB batches.
I pitched my yeast when the thermometer read 112F because it had been cooling for a while and I knew it was wrong (was giving me 90F for room temp). I definitely didn't kill my yeast, though most likely pitched too warm as I was dealing with a near krausen fountain at 4:30 this morning.
Considering that the readings weren't just off but were fluctuating wildly, I expect it's more than just a calibration problem.
Can y'all recommend a simple, accurate thermometer that I can purchase?
I find that I don't use the alarm setting of this digital one, so an analog model is just fine.

I was listening to a Jamil show a while ago and he said that he wished they'd just sell thermometers that were labeled with A B C D E and were consistent. Once you know your pale ales turn out great at B.5 you just keep your mash there. It got me thinking. Consistency is even more important than accuracy.

To that end, I try to get once thermometer that is at least consistent. If I use more than one thermometer, I check it against that one. I currently use a thermapen for that. I don't really know that its completely accurate, but it has a good reputation and I feel that it is consistent. It's also expensive. I love it, though. I use it daily for cooking, too.

You might consider using a glass lab thermometer as a reference thermometer and calibrate a non-breakable one off of that. You could use it in the mash, but I'd be a bit worried about breaking it.

I'm thinking about something like http://www.amazon.com/dp/B001BLOJGI/?tag=skimlinks_replacement-20