I just came across the datasheet (I don't think the chip itself is in production yet) for the PIC12F639 which has a three channel (diversity antennas?) Low Frequency Analog Front End tuned to 125kHz with 3mV sensitivity.
I haven't studied it in depth as I'm pretty much occupied by roZetta at present but, at first glance, it looks like it might be used for direct detection of X-10 PLC using the Carrier Clock Detector (even though the AFE is intended for wireless applications).
It can also use Microchip's Keeloq crypto module.