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I use TV Player for Spotify: https://play.google.com/store/apps/details?id=com.sregg.android.tv.spotifyPlayer It's a free app that works pretty well, the only downside is that it's a bit of a pain to go from your playlist to the player controls. There's Emma for Spotify, which has easier access to controls but it limited in the ease of finding content, esp. in the free version: https://play.google.com/store/apps/details?id=com.alexfillips.emmaTV
So https://twitter.com/nvidiashield/status/635841593048756224 from August 2015 and the image showing 'Amazon Instant Video' and 'Spotify' ( https://pbs.twimg.com/media/CNL2j0iUcAEdk6N.jpg ) is still up, as is http://shield.nvidia.com/blog/new-channels-coming-to-shield from the same date with 'Amazon Instant Video' 'Stay Tuned!', although 'Spotify' 'There is also a TV Player for Spotify App on the Play Store.' (TV Player Spotify: https://play.google.com/store/apps/details?id=com.sregg.android.tv.spotifyPlayer ), which is unofficial, is still all that is available and "... cast the hugely popular Spotify Music from Android and iOS devices to SHIELD soon." from late September 2015 ( http://blogs.nvidia.com/blog/2015/09/30/shield-geforce-now-google-fiber/ ) yet to materialise.
However, as of January 2016, there has been no further update ( http://blogs.nvidia.com/blog/2016/01/05/shield-android-marshmallow/ ).
Meanwhile, Amazon Video support on Android TV is extending from Sony TVs to Philips / TP Vision:
> The range of video streaming options will significantly increase in the first quarter of 2016 with the addition of Amazon Instant Video service to the Philips Android TV platform to coincide with the launch of the first 2016 Philips TVs.
> The service will offer Full HD streaming to all Philips Android TVs with the option of 4K UHD streaming to specific Philips 4K sets – models to be confirmed shortly.
and
> Philips Android TV to offer console quality games from Gamefly, all streamed via the cloud
> In addition, the Philips Smart TV platform will also offer a new subscription games service, Gametree TV Gold from TransGaming, which will offer the ever popular games Rummikub, Tetris and WPT and more!
http://hexus.net/ce/items/audio-visual/89360-philips-tv-ces-2016/
> Games ranging from Tetris to Texas Hold'em means there's something for everyone. The GameTree TV standard free-to-play collection of favorites continues to see rising adoption internationally and will remain available to all players supported by in-game advertising.
> Alternatively, the entire GameTree TV Gold collection, with a new title being added to the catalog every month for subscribers to enjoy, will be offered at less than US$5.00 a month.