Reachability is an often-under-appreciated feature of iOS that makes it so much easier for iPhone users to touch interface elements normally residing at the top of the display – especially when only using one hand. For the most part, it does a good job of this.
Unfortunately, Reachability also tends to leave a lot of unused space at the top of the iPhone’s display when it moves the interface down to make it more reachable with one hand, an issue that a newly released and free jailbreak tweak dubbed ReachInfo by iOS developer 1di4r tries to fix.