NPM does have built-in integration with NotePager Pro (SMS Messages Anywhere, at Any Time) which would allow OOB dial-out to a number. If I am reading correct, you are also looking to take feedback from the receiving device to clear the alert correct?
Correct - at a minimum I want to know if there is an answer from the number dialed. If feasible perhaps I could gather other data from the device as well.
I'd then like to take further action based on the result, such as clearing the alert, updating device properties, sending an email to specific people, updating an internal ticket, etc.
The first step of course if getting the feedback from the dial attempt...
My suggestion would be to write a [powershell?] script that would perform the action you needed and set a custom property; SWO could then use the custom properties to trigger other alerts.
e.g. dial the modem
if a reply then set a custom property to one value
if no reply then set a custom property to a different value
I posted a powershell script the other day to set a custom property from a syslog or snmpTrap; it should work from an advanced alert as well, all that would be needed would be a way to script up the phone call.