Leadless, implantable microstimulators for treating chronic inflammation. These devices can include a static magnetic field detector (e.g., non-Hall effect sensors/detectors, including those based on a Wiegand effect or generating pulses at a predetermined frequency range and using a detection circuit to determine the decay rate of the pulses), to trigger an emergency shut off of the microstimulator. Also described are methods and apparatuses for regulating the temperature of an implant based applied power from a charger (e.g., voltage across the charger when unloaded and when loaded by the implant) to yield a power control loop correlated with the power drawn by the implant to determine temperature of the implant. A negotiation protocol can exchange data between the charger and the implant (e.g., type of charger, type of implant, nature of the coupling between the two, etc.) to set target power control loop parameters to estimate and regulate implant temperature.