There isn't a JRiver iPad app! There are some third party ones (e.g. JRemote, MyRiver), but JRiver have only developed Gizo which is for Android.
If Theater View could be overhauled to be more attractive and useable on touch-screen devices then you could actually install JRiver itself as a client on a Windows 8 tablet, that might be a more appropriate route for JRiver to go down rather than developing a complete new app.