By our count, the first Windows Phone 7 third-party app to take advantage of Live Tiles is WeatherBug, a free weather application that is now available in the Marketplace. It not only pushes current conditions to a Live Tile, giving you glaceable information, but it also uses the push notification service in Windows Phone 7 that will give you a toast-style notification if there is severe weather in your area. The app itself is similar to The Weather Channel WP7 app: it shows you the forecast, lets you look at an interactive radar map, plus play weather videos. Hopefully this is just the start to third-parties taking advantage of Live Tiles!
Update: Turns out that you can specify how often the Live Tile is updated. The lowest interval is 20 minutes, the highest is four hours. Obviously the lower the interval, the more it’ll use your data and drain your battery.