ACR Satellite 2 406 EPIRB (MBEA10) - $399 from Johnny Appleseed GPS
They're selling them at this price because they've had the units sitting around for the last 15 months. The battery life is good for another 3.5 years and they're changeable in any case.
Has all the various bits you want - auto activate, strobe, operation on 406 mhz.
Price your looking at elsewhere is $500 (on sale) to $700.