It is possible to use LinkedIn InMail to send video messages to your prospects.
You will need to log into LinkedIn InMail and select a contact, then paste a link to the sharing page of the Vidyard Player into the text box. When this renders on the recipient's screen, they will see the thumbnail of the player that links to the sharing page.
Note: You may find that the thumbnail does not render when you look at the sent items, but based on our tests (Feb 2018) the recipient will see it.
The 'Share to LinkedIn' option that you can use in the Vidyard Platform is a standard LinkedIn sharing option. This does not have the compatibility with InMail to show contacts that are not already in your network.