If you are looking to install Cydia apps on your iPhone or iPad I suggest you download Cydia. Cydia is the main and popular third-party application manager and with account logging for storing payments for apps it is similar to App Store. Since any iDevice is limited the only way to install Cydia is by jailbreaking.
The majority of apps present in Cydia are free and you can easily extend the apps catalog by adding repositories. Cydia comes loaded with tweaks and themes that can change the visual appearance of your device or how will you interact with it.
Examples of Cydia apps:
For example if we are looking to change the appearance, WinterBoard is the perfect Cydia app to do the job. With it you can change the graphics of your status bar, change the icons, make changes to applications, install themes, change the wallpapers, and customize the ringtones or sound notifications for your device.
As for the interaction with your device Activator is a good example. It is one of the most popular Cydia apps for any iDevice. With this ap you can easily assign or customize any button for example to turn on/off Wi-Fi or Bluetooth.
Another important app that you must have on your device is iFile. iFile allows you browse the file system of your device. You can even access files to view or edit them. It supports sound, movie, text files. It’s also an audio and video player, a document viewer and editor. It can also manage archived files. This app can be downloaded for free from Cydia.
Dashboard X is a small and popular Cydia tweak. This tweak lets you place widgets on your home screen. This tweak is not free it costs just $1.99.
As you can see there are many tweaks and apps that may interest you the only thing that you need is time to test them.