I think you might be looking at doing this either from the server side or you'll need an App different from the inbuilt one.
A Google search showed me you can install pretty much everything that is available on Android, so you should be able to find one where you can specify the subnets that should go via the VPN.
Hope this helps!
Please keep in mind that what I post here is my personal knowledge and opinion. Don't take anything I say for the Holy Grail, but try and see! Appreciate who helps and be respectful of every opinion and every solution offered. Share the love, especially the Meraki one!