The DD-7 also has a built in tap tempo function, but like the echo park it requires that you hold the footswitch down for a couple of seconds to use it, which I just don't find practical when I need to adjust it on the fly. I believe the flashback uses your audio signal to set the tempo: you hold the switch down and literally tap your strings - in other words not an option to use mid-song.
Not true, echo park has a switch that you tap lightly for tempo and press harder to turn pedal on/off. Should be easy once you get the hang of it. You can tap tempo when it's off too.
