They're accurate enough and have the ability to be calibrated. Not sure on the battery life...
For your purposes, a probed Accurite would likely be a better choice. Remember - a thermostat does not tell you the temperature of the hot spot. It only controls the amount of power being sent to the heat source. You still need something to make sure it's doing its job properly, which a probed thermometer would do. There are Accurite models with probes that also read ambient temperature and humidity at the unit itself that many people (including myself in the past) use successfully.