Another unofficial app that is a good reason for many people to jailbreak their iPhones is xGPS, a free turn-by-turn GPS app.
For pre-iOS4 iPhones, you had to jailbreak to be able to run background apps from third parties (multitask).
Rooting your Android phone can drastically improve its performance if you install a custom ROM that has been tweaked for performance. You can find apps that will overclock the phone’s processor, but you must have root in order to install them.
With some phones, you may have to root in order to install programs on the microSD card. Android 2.2 adds that ability, but some carriers may disable it.
Some custom ROMs add support for proxy and VPN.
For iPhone and Android phones, you’ll need to jailbreak or root the phone in order to run programs that let you turn the phone into a Wi-Fi hotspot so you can connect your laptop or an iPad to the Internet through its 3G or 4G network without paying an extra monthly fee to the carrier. This is something you can already do with theWMWifiRouter app on a Windows Mobile 6.5 phone (without any jailbreaking required) and that was, for m