I dunno, guys; thermalmonitord is a 'daemon'; i.e., a task that runs in the background and, as the name implies, it's job is to keep an eye on the thermal sensors. However, in most cases where the direct communication with the sensor has failed, it will tell you which sensor it was that it can't talk to.
In this case, though, what I'm seeing is that trying to talk to the thermal monitor daemon failed; the call to ask it for information returned a status of "not alive" after it failed it's periodic check in. So in this case it's the software that checks the sensors that has failed, rather than one of the sensors it's supposed to be checking.
That is specifically a software problem, not a hardware one, so replacing hardware won't fix that problem except indirectly. The things is, we don't know why thermalmonitord crashed; it could be corrupted firmware, bad NAND memory, or some other hardware factor we don't know about.
So whenever you have something you know to be a software error such as this, the first thing to do is to do a restore or update of the operating system in order to replace any corrupted storage with a good copy. After that, you check the phone and see if it's working again; if not, then you have to start looking at hardware issues.
@flannelist Alisha, you're obviously experienced in iOS/Linux internals; what do you think?