Some of the last Panasonic Plasma's were "smart". I have a 50" I picked up last year that is Smart. The problem with putting the "smart" in a TV is that when the manufacturer stops supporting it in a few years, you're screwed. I would recommend buying a something like a Roku or AppleTV. That way when the manufacturer stops supporting it, or they come out with something way cooler, you can toss it and your only out like a $100. These set-top-boxes are so small, they can be Velcro-ed to the back of the TV. Some of the "stick" versions draw power from USB of HDMI so no power cord needed. Another alternative is a "smart" Blu-ray player.
Also, if you're using "Smart" in a TV and have it hooked up to an AV receiver, you might want to check if they support ARC (audio return channel). This allows the audio from the Apps to run over the HDMI cable back to the Receiver which means one less cable to worry about.
I have a friend that travels a lot. He uses a Google Chromecast for Netflix and Amazon Prime; so small it slips in a shirt pocket.
Hope this helps,