While Samsung has cooperated with DirectTV for 4K content, Sony has introduced a couple products for delivering 4K content for its Bravia 4K Ultra HD Smart LED Android TV's .
For those wanting to make their own 4K content, Sony offers the 4K Ultra HD Camcorder.
For those just wanting to kick back and watch Hollywood movies, Sony offers the 4K Ultra HD Media Player- basically a large hard drive that can download 4K content from Sony. This Media player is a strange beast though. Sony does not allow Best Buy to actually demo this Media Player for some reason. Huh? This Sony Media Player also only works with Sony 4K TV's or UHD TV's that support HDMI 2.0 and HDCP 2.2.
With time, these issues with trying to find 4K content will be sorted out. However, sometimes you feel like many of these companies are just rushing out 4K when things aren't really ready making it frustrating for the buyer when they realize 4K is just not a reality yet.