would you even need an additional battery ? why not use the current battery and circuit to shutdown the phone earlier limiting the functionality to low powered 15 minute beeps, no screen display and only enough power for one 999/911/112 phone call

Yep, that works, was the original thought infact, but it may not be as reliable. Furthermore, may not allow the "always on" functionality of a mini circuit for the locator/noiser/page feature, (so you can always find your phone, even when it annoyingly turns off!)

Hence the opt-ing for the present idea :)

I have to agree with Daren. I don't think a second battery would be any more reliable than a regulated single battery. If anything, the single battery would probably be more reliable.

I'll go with the majority and agree, as I have very little experience in electronics really speaking.

Do you however think that the idea could be commercially viable, that's where the issue has apparently arisen?

It sounds reasonable to me.

When a cell phone shuts down, the battery is not fully discharged. A small circuit could use that power to "chirp" periodically until either the cell phone is put on the charger or the battery is pulled out of the cell phone.

Just what we need to make the cost of the phone to go up even more. If you have problems finding the phone do some cleaning up so it is not hidden under old mags, old news paper--or get into habit to put it back where it belongs on its base--problem solved.

Sounds like CSM just had the wonderful experience of paying for a new phone.

I like the idea. I agree that one battery is better than two. If your primary battery (in a two battery device) goes bad, you know this immediately when you try to use your phone in the normal course of the day. It sounds like the backup battery would sit unused until needed (when the phone is lost or you needed to make an emergency call) which is exactly when you don't want to find out it has failed/gone bad.

My current phone begins to emit a periodic chirp when the battery power is low. I think Daren is correct that if you simply shut the phone down completely earlier while there is still enough of a charge to make the finder and emergency call features work then you have a useful idea. I like it much better than the periodic chirp which ultimately drains the battery. The chirp does me no good if I'm at work and the phone is at home and it chirps itself dead before I get home to hear it.