Since the shield is cast-enabled, and is built on Android TV, shouldnt the slingplayer apps cast to the shield? I cant guarantee the quality of this method, since the cast implementation on a regular chromecast is terrible and sling refuses to fix it. But theoretically, per all the advertisements from sling and nvidia promoting google cast, it should work. Wouldnt surprise me if it didnt, though....sigh....
I have a shield, and the cast feature is very flaky. The stream usually takes few tries to start up. And once you have the stream going , about 3 4 minutes into the stream, you lose half of the picture . I haven't had a consistent behavior on nVidia Shield or 2nd gen ChromeCast.
Somehow, it works well with FireTV and FireTV stick. I wish there is a dedicated app, rather then an inconsistent cast feature.