There is the 4 tuner Next Gen ota dvr: Tablo that record 4 shows at the same time. There is also the more expensive 4 tuner ota dvr: AirTV Anywhere that can be used with or without Sling TV. I have both of them and they work reliably and the Air TV Anywhere ota dvr can integrate into the Sling TV app and it is all in one place. Even if you have no programming with Sling TV there is Free Sling channels that you can watch with ads. I prefer the TABLO if I had to pick one. It has a good interface and is easy to use and no monthly fees for the Tablo or the Air Tv Anywhere device.
www.tablotv.com
www.airtv.net/products/airtv-anywhere/
***You can buy Air TV anywhere device from Amazon too. If it no longer is offered on the Air Tv website.