I think your exchange or email server transports rules are your best solution. With that said, we do not use the lansweeper help desk as we had integrated samanage before buying lansweeper. If lansweeper sends out email alerts, your trasport rule can include something like subject line includes "ticket:**** Priority: Emergency" send message to: distribution groupX@domain.com
The distribution group should include the sms address contacts of your help desk staff verizon for example is 5552221234@vtext.com for plain text sms You can also do mms for pictures/etc. Each of your help desk staff mobiles are setup as contacts (hidden from GAL) and memebers of your distribution group. Again, I am not familiar with lansweeper's helpdesk but this is how we have our sms alerts setup for critical/kid glove alerts. Good luck!