Three of the most highly rated apps for playing bridge on iPhone or Android are FunBridge, iBridgePlus and WeWeWeb Bridge. The first two are for iPhone only, while the last one is compatible with both iPhone and Android.
FunBridge has a very high resolution, making it a good choice for people with sight issues. It comes in a variety of languages. This app must be purchased, but it is popular with over 200,000 players online. iBridge has an arcade-style look and is designed to appeal to younger users. WeWeWeb Bridge has more complicated gameplay overall, but it is free to download and quite highly rated.