ACK Technologies finally got their 406 MHz ELT approved. They've been working on the approval for well over a year, and every time it looked like they were getting close there would be some issue with the interpretation of the test results that required another retest.

I've ordered one to replace my ACK 121.5 MHz ELT - it should ship as soon as Aircraft Spruce gets them in stock. I've already run the wire under the floor to feed GPS position to the ELT, so it hopefully shouldn't be too big a job to install it.