Just to set expectations, the handy Citymapper app works in 13 cities, only five of which are in the U.S. (New York, Boston, Washington, Chicago and the San Francisco Bay Area). And it doesn’t provide voice-prompted, turn-by-turn directions, as other GPS navigation apps do. Instead, it shows your route on a map, which automatically updates as you go via GPS. The free app has its quirks, but during a recent London trip, it turned out to be the most reliable option I tried, in terms of accurate pedestrian directions. In addition to pedestrian mode, the app includes routing for public transit, cycling, and taxi rides. Unfortunately, there’s no option to download city maps to your device, which would be great for international travel.