XML push client/phone intiated?

[jolouis]

Honestly it really sounds like you are going about this in a strange way. If the idea is to let customers know there is a problem and avoid support hours wasted when you have something going on, rather than using an XML message (which people might miss, dismiss, not read, etc) the typical way is to have an automated message inserted into the support queue. Advantages:
1) Only people who experience a problem will call in. Your outage/issue/whatever may not affect everyone, or not everyone in the same way. If you send out generic "Sorry we are down right now please wait" kind of messages, it highlights the problems with your system to all users, even those who might not have noticed (i.e. they weren't using their phone during the 5 minutes you were down, so would not have cared, but now see a message telling them about the error and your lack of reliability). The more that happens, the less confidence customers will have with your setup.
2) When people who experience a problem call in, they should hear the automated message immediately (i.e. "As of ZZZ time we are experiencing an outage that affects customers in YYY area. The problem is expected to be resolved by QQQ time. If you are in this area and experiencing difficulties please check back/check our website/whatever for updates. Our customer service staff does not have any additional information on this issue as of yet"). Just hearing that message will get rid of the majority of your complaining customers as they will simply hang up and wait. Most people just want to know that you are aware of the issue.

Anyway enough about how to properly run your organization...

At this point you have all the information you need from a Yealink perspective. If you don't know how to generate SIP Notify messages check with your PBX vendor/supplier/support as it should be a built in method. From there you would just need a way for all PBXes to check status from a central server and send out notifys as required... but if the PBX crashes or something that wouldn't work, and hence you're back to realizing your approach is not the best option...