Chains accumulate a lot of dirt and grime which, if ignored, turns into a very costly grinding paste particularly on multi-geared derailleur systems. Cleaning kits of this kind are not a new idea, although this seems to be one of the better designs. A chain bath clamps to the chain cleaner aerosol and a flexible hose feeds from the nozzle, directing solvent into the reservoir.
Place the chain within the chain bath, and pull the Chain Doc trigger to engage the bristles against the chain. Spray solvent into the bath continuously while rotating the cranks backwards until the chain runs through clean. The solvent acts fast, making short work of a grimy mountain bike chain, although be warned that dirty solvent can seep from the bath while you're washing your chain so this is best done outside.
While traditionalists might argue a 50/50 petrol/diesel mix and 'radiator' paint brush is considerably cheaper, this is arguably much better for the environment, and is less messy and time consuming, especially if you have a fleet of bikes.