I use a weber style BBQ wireless thermometer for mashing, checked it against 2 other digital thermo's and if they are inaccurate at least they are all out by the same amount lol.
It has a probe which sits in the pot, with the lead tied around pot handle to keep the probe in place (braided wire lead Dosen't like being submerged) the sender sits on the gas bottle, the receiver can be carried around (on your belt if you're that way inclined
) has a range of 50m or so and has preset selectable alarm points (rare, medium, well for different meats) which don't correspond exactly to common mash points but are close enough to work with.
Was looking at fixing a dial thermo to the pot but was worried about fouling the bag (snag in a bag?) When stirring and lifting, and using this gives me constant readings without having to unwrap the blanket all the time to check.
Another benefit I found is I can add heat halfway through the mash, or even do a full step mash, without having to hold a thermometer in one hand and stir with the other, and not overshoot temps.
All this for around $50, and you can use it to cook a perfect roast pork at no extra charge... Once the boil's started of course!