A note should be added to this.

It may not be legal for boaters, hikers, hunters or aircraft owners (not
sure who is left). Although I suppose you do not care if it is a true
emergency, if you use it and it is later determined it was not appropriate,
you may have a legal problem.

Also, the satellites will no longer pick up 121.5 or 243 mHZ after 2009.

Personal units that are now being sold contain digital imprints so you can
be identified and some even have GPS coordinates - but they are not cheap.

The unit is cheap and I do not want to discourage a bargain, but do not use
it in a situation where your life depends upon it.

Replacement batteries can be very expensive - unless you want to make your
own pack.

But, hey, it is only $25.