For pan searing, a quick and accurate thermometer doesn't actually make this much easier. I also have a Thermapen, but pan searing to a certain level of doneness is still a bit of an art because the final interior temperature after resting can be quite a bit different than the pull temperature due to residual heat at the edges of the meat. Even trying to get a consistent interior temperature using the same pan temperature (using a Control Freak induction cooktop) is difficult because the shape, thickness, and moisture content of meat can vary significantly. There's a few new gadgets that attempt to resolve this (e.g., this predictive thermometer with 8 sensors https://combustion.inc), but honestly having a lot of cooking experience is probably the best way to get a feel for when to remove the meat from the pan under rapid cooking conditions.
Of course, sous vide and reverse sear are completely different and while you can indeed get a precise temperature, those methods have their own trade-offs (namely, it's difficult to get as thick of a crust).