Note that Redpower isn't in FTB Unleashed so this won't be relevant unless you are using a newer pack with "Project Red" logic in instead.

Also note Railcraft adds a "Capacitor box" that can also pulse-stretch. It can be paired with a controller or directly triggered by a redstone repeater.

This is one of the tougher devices to understand from the wiki description, so I'll try myself. In logic terms its a kind of "monostable" latch.

Its two most obvious functions are:

Placing in a chain to make a control sequence (improved sequencer). Each cell in the chain can have a different delay set.

Using singly to convert a 1-tick pulse into a decent length pulse. (monostable)

In its default placement it has a trigger input facing you. A pulse here will set it going.

Once triggered a timer starts running for the time you have set.

It has a main (or most useful) output to the left that will output a long pulse for the time set.

It has a chain output facing away from you that outputs a pulse when the time ends, and could be used to trigger another state cell.

It has an additional input to the right that restarts the time delay and makes the output pulse longer, but will NOT trigger the cell if it is not already active.

Note a prolonged redstone input on the main input will jam the timer, it will only start timing after the fall of the trigger signal.

maybe a screenshot of one you made?

Not actually in operation, but I hope this shows the shape of the device and where the inputs and outputs are.

I'm facing the trigger input, the chain output is the one that can trigger another cell.

Used as a pulse-stretcher it bends the signal round a corner, though oddly enough in some flow control applications that may be what you need.