Sling Media's parent company, Echo Star also owns Dish Network. The only "Sling Loaded" DVR that I'm aware of is the Dish Network ViP 922 (http://www.dishnetwork.com/receivers/dvr/default.aspx) satellite receiver. Honestly, though I don't recommend it. Not only would you be tied to their satellite service but its the first generation stuff that seems to have problems of its own.
You can use the Slingbox in conjunction with just about any DVR. The DVR will timeshift the shows, while the Slingbox can placeshift the video content. As long as the DVR has compatible video and audio outputs then the only question of compatibilty is whether the IR Blasters will allow you to control the set-top box remotely.
You can use the Slingbox Setup Assistant (http://support.slingbox.com/get/KB-5000164) to find out devices which have offical support. If the device you're looking for isn't listed there then this article (http://support.slingbox.com/get/KB-2000299.html) will help you with alternative resources for custom remote profiles.
I'm currently using the a DVR provided by Time Warner, it is the Scientific Atlanta 8300HDC. It works very well in being able to record my programs, and I can watch them using the Slingbox in an alternate location.
If your current television provider has an option of a DVR you could opt for it. I was actually looking to buy my own DVR, and did consider a consider a TiVO. Unfortuantely, their subscription fees wouldn't have saved me money from leasing the DVR from my cable company. I found a better alternative called the Moxi (http://moxi.com/us/home.html), it offered better expandability without added subscription fees and at a lower cost. You might consider it over the TiVO.