[andy]

There seems to be a paradox between the thread title and what the OP is saying, as the discussion seems to be mainly about web-based callback, and it being redundant when making outgoing calls from a wi-fi zone.

Not everyone has expensive wi-fi phones, or wants to able to call an ATA and Asterisk set-up at home, either as callthrough or even trying to develop their own callback platform.

Hence the mobile callback, which does not need ordinary internet access, only wap/gprs, and can be used with almost any modest mobile phone.

There are any number of circumstances where it is highly useful as it stands - using any mobile or landline at other than their own tariffs, especially those global SIMs that have free incoming roaming calls in many countries, or landlines with outgoing calls barred

I will be driving through Europe next week; the motorways do not have wi-fi access, and I know of no way of using an ATA in the car. When I am visiting three company premises and two hotels, I don't need to get wound up about setting up internet access. I'll have free incoming calls on my mobile phone, and use callback to call home for a few pence a minute. On what I've read so far, the OP does not use a mobile phone much in similar circumstances.

Though the suggested ANI callback could be useful to some, not all phones send caller ID, so instead would need a dedicated DID per phone used on an account, thus extra overheads.

The only addition I would suggest for the mobile callback system is to be able to enter a number that has not been predefined in the phonebook.