Since we are a skype for business shop with several lifesize rooms many of our users prefer to connect from their desks using sfb. We have been manually adding the meetings sip addresses into the into the invites and asking users to either click on them or copy and paste into skype dialer. If the sip:email@example.com url could be added to the invites themselves it would take quite a bit of manual work out of the process.
There is of course the "call from a 3rd party app link" but it is buried in a 2nd page which is not really handy or intuitive.
Created from this discussion: Skype link in Lifesize invite