Interesting that they're the first of the fast food chains to get mobile ordering. I'll admit, the idea of being able to pre-pick your food (and pre-pay) is kind of cool. Panera and a few other "fast casual" places already have systems like this, although I haven't tried them myself.
The thing that seems odd here though is the "we won't make it until you arrive" part.
If you're eating Taco Bell, don't you automatically expect it to come from an industrial sized steam tray, get assembled, and then wait for you under a heat lamp, just like the food you'd get if you placed your order in the store? What's so different about the food that gets thrown together once you arrive?