It’s aptly called QuickScroll 2 and it is available on Cydia for users who have jailbroken their iPhone.
QuickScroll is developed by KennyTM who has developed some very good jailbreak iPhone apps like hClipboard, which was the best "Copy and Paste" solution before Apple introduced the feature in iPhone OS 3.0 and 5-Row QWERTY keyboard, which was extremely popular with our readers.
Once you have installed QuickScroll on your jailbroken iPhone via Cydia, you can activate QuickScroll scrollbar with a single tap. You can change the activation to a two-finger or three-finger tap or scrolling by launching the Settings app and going to settings for QuickScroll application.
Once activated, you will see a horizontal and vertical scrollbar as seen in the screenshot below:
QuickScroll also supports paging for PDF documents, which is quite neat. Here is how it works:
Activate the scrollbar like above.
Press the "123" button in the lower-right corner as seen in the screenshot below.
Enter the page number in the new dialog.
You can also jump home screens on your iPhone using this feature (though it considers the Spotlight for iPhone as the first home screen).
You also have an option to turn off the scroll bar via the Settings app, which enables a 2D scroll pane as seen in the screenshot below.
It's a cool feature and you can use it as a trackpad but I found the scroll bar option more functional.
You can disable the QuickScroll feature in iPhone apps that you feel the feature is unnecessary again via the Settings app.
QuickScroll is another superb jailbreak iPhone app by KennyTM and one that you should definitely check out.
As always, let us know if you liked it.