This is just an idea for a usefull script for companies that do not show/have direct phone numbers for local extensions. I do not have the insigth/experience to build such script in asterisk. Here goes:
An employee calls a truck driver to get status of a delivery. The driver is in the middle of handling a packet and is unable to answer the phone. Shortly after, the driver has time to attend his mobile phone which displays a missed call. He dials back and get the companys IVR - the driver has no idea who he should be talking to.
Instead of sending the driver to the IVR, the pbx should recognize the drivers phone number and route the call back to the extension that tried to call him earlier. The script will need to take care of stale entries - calls older than, say, 1 hour should be ignored and the call routed normally.