I've found NetExtender (Packaging NetExtender for Munki) to be a little less buggy than SonicWALL Mobile Connect, but NetExtender is pretty much non-functioning in El Capitan, so I'm looking at possibly deploying SonicWALL Mobile Connect in the future.
The import process into Munki for the .app is fairly straightforward. You install SonicWALL Mobile Connect from the Mac App Store and then import the .app using munkiimport.
If you want to then deploy as an update a profile so you don't have to tell users a server name, you can create a profile using Apple Configurator (thanks to Greg Neagle for this tip). Profile Manager in OS X Server is another option.
Once you've selected VPN, click Configure to configure the profile.
It's okay to leave the username and password blank.
You may get a warning that there's an error in your profile (perhaps it's looking for the username and password). I have tested the "error"-giving profile with all the mandatory fields filled in, and it seems to still work.
Once that's done, you can use munkiimport to import the profile and make it an update for the SonicWALL Mobile Connect app.