Navigating Houston airport - Global Entry/TSA Pre-check?

Last time I checked DTW required an appointment. Mobile Pass, which is free, works just fine. It's an app you can add to your phone. All you do is scan your passport info into the app and access it when you return from another country. You can do this while you're taxiing, filling in your airlines and flight #. You then get a bar code type pass on your phone to go through a special line at Customs , which so far has been much faster than the general line. It's not accepted yet at all airports but can be used at the Houston airport.