This is a pretty simple command that I have found many, many possible applications for.
The premise is simple: the command syntax is "/wait <wait interval> [time of signal]" where the wait interval and time of signal are in ticks.
When a command block with this command is powered, it will pause for the specified wait interval and then output a signal at full strength via comparator, for as long as the specified time of signal is; if unspecified, the length of time that the signal will be output will be 10 redstone ticks - one second, the current length of a button.
This would be a lot more helpful for creating long command sequences that take place over long periods of time, such as credits on an adventure map or delayed-delivery items and buffs in a minigame, without using up a lot of space with long repeater chains that can often be confusing and tedious to create.
This has probably been suggested before, but I agree that this should be implemented. Especially since I am frustrating myself with trying to create a long and compact repeater chain myself in a custom map.