Replying to Airbag

Hi,

I am looking for one of those backpacks you can wear which contain an airbag, that can be released in the case of an avalanche.

Anything you can tell me about it would be great suggestions for whatever models may be good or bad, companies which make them, etc. There is no price limit, I would just like to know as much about these as I need to.

Oh and this isn't for myself, I don't ski anywhere near enough to even consider this.

Thanks for any help!