At this time, there are no applications for Smart TVs specifically. You would need a connected device still, for example the Amazon Fire Stick or Roku. The Amazon Fire Stick would have you download the SlingPlayer Application and log in to stream, the other supported connected devices need a mobile device (a phone or tablet) in between to mirror the signal from onto the TV. I've linked an article below that goes over the compatibility options between the Slingboxes and the Connected Devices:
I hope this helps!!