I think this only works with HD boxes. I've got 3 boxes, an HD DVR, an HD and a regular SD. I only seem to be able to control the 2 HD boxes.
There is a DirecTV app for Android and Apple. I've got it installed on my Android based phone, and also on my iPad. I'm not sure how an iPhone would compare. On my phone, I can search the guide and setup DVR. On my iPad, it's a whole different beast. I suspect that the iPhone would not be quite as nice as the iPad, but I don't know for sure. On the iPad, you can setup multiple windows with your "favorite" channels such that you can see what's currently playing on each of them (much easier than looking through the guide using the regular remote). It'll display what you're watching. (I get to select which of the 2 boxes I'm watching) From those "favorites" views you can poke a channel and it will allow you to either change to that channel or record the show. You can also browse the guide listing the channels either alphabetically or numerically. You can go to sections of the guide based on the leading letter of the channel (alphabetically) or to the number every 50 channels (1, 50, 100, 150....). Not only that, but you can click a button that pulls up the major functionality of the actual remote and control the "box" from your ipad (menu, guide, list, etc....).
In my short period of experience, it's much easier and faster than using the remote. The only issue is that you have to have the "right" boxes, have them setup correctly (under setup, you have to have "external devices" set to "on"), and you have to have an iPad.
The pics below I found on the net. In the first pic, there are 3 pages of options. You can add/remove/change the options and where they show up. For instance, I got rid of the "sports programs" column on the right.
