There are a number of delay effects apps available on the iPad, many of which are only part of a synth app that has many more effects alongside. Most of these apps are designed with the older iOS theme in mind. That is, they tend to look more like a real effects pedal and less like a digital program.
Vandelay by Klevgränd is not afraid to take an effects program into the iOS 8 design scheme. It is heavily based on multi touch gestures and looks absolutely nothing like a real life delay board, and that’s a good thing.