If you have a VPN configured on your iOS device that you like to use for specific applications while on public Wi-Fi networks to help ensure your safety, then you might be able to make great use of a new free jailbreak tweak called Auto VPN
by iOS developer Cylay.
With Auto VPN installed, you will be able to have your device's configured VPN toggled on and off on a per-application basis. In other words, the tweak will let you pick applications that you want the VPN to be automatically enabled in, and when you open those applications, the VPN service will be enabled. As soon as you close out of those applications, your VPN service will be disabled again.
The tweak will add a preferences pane to the Settings application where you can configure a few important settings:
From the main preferences pane, you can enable or disable Auto VPN on demand, as well as pick the applications that you want your VPN service to be enabled in, and then choose how long after closing the applications you have selected that the VPN service should be discontinued.
Notably, you can only pick third-party applications from the application selector, such as the ones you download from the App Store. You can set the VPN service to disconnect immediately, 5 seconds, 30 seconds, 1 minute, 5 minutes, or never after closing an application that you have the tweak set to enable the VPN for.
The tweak doesn't come with a VPN service, so you'll need to configure one beforehand. There are plenty of VPN options available in the App Store, such as Cloak, TunnelBear, and more. Once configured, you can install this tweak and get started.
If you would like to give Auto VPN a try, it's available for free right now in Cydia's BigBoss repository.
iOS 7.0-7.0.6, VPN
iPhone 5 running iOS 7.0.6