Never heard of such a thing (the OP), and consider it unnecessary too. I clean my beer lines at the same time that I clean the keg that just kicked. Process follows...
Remove empty keg from brew fridge (disconnect gas and beer QD's).
Rinse keg out with hot tap water 2-3 times or until looks clean.
Mix up 1-1.5 gallons of PBW in the keg with hot tap water. Pressurize and shake the living hell out of the keg.
Let rest ~10 minutes.
Connect to gas feed and to liquid ball lock that same keg was using.
Push 1-2 quarts of PBW under higher pressure (20-30psi) through beer line and faucet. Leave PBW solution in beer line to soak for ~10 minutes.
Drain keg and rinse completely.
Put about a gallon (no more than two) of water into keg and wait for beer line soak time to end.
Send clean water through beer line under high pressure to rinse PBW out.
Put 2-4 quarts of StarSan solution into keg (already on hand/mixed since I have a bucket mixed pretty much all the time), shake and pressurize keg.
Send 1-2 quarts of StarSan solution through beer line under normal pressure and leave in with solution in it.
I sometimes leave the StarSan in the keg, other times I'll drain it out and store the keg 'dry' until it's time to fill it again. I always leave it with some pressure in the keg (about 10psi).
When it's time to put beer on that tap (typically once I've sent the StarSan through the lines) I just pull from the tap until beer comes through, then discard the couple of ounces of StarSan/beer mix. Then it's time to start enjoying the next brew on tap. Total time to clean out the lines, and keg, is maybe 30-45 minutes, depending on how long I let each soak/rest last. You could go just a couple of minutes. I usually just let the soak/rest happen while I'm going to the next stage. If I don't think enough time has passed, I pull a pint of something that's still flowing and relax.
I do have three faucets in the brew fridge door, and spots for four kegs. This means I have one keg carbonating while I'm able to drink from the other three. :rockin:
I've seen the differnt line cleaners, but not like the above linked one... Might have to look into making one of those later. Although, since I'm cleaning my keg anyways, I might just keep with my current method. I'm really just running the clean/sanitize solutions through the line before discarding.