In spite of its size, it appears to be only half a Dishmaster. What PITA that thing would be to install onto an existing faucet already in place, and it's so prohibitively bulky. Just the amount of fittings and potential for leaks in replacing the existing faucet's spout assembly would trigger a 180 if I were shopping for something like that.
If memory serves me, Elkay made something similar to a Dishmaster, but I don't recall if it was a complete unit like a DM or just the spout replacement like Gerity.
Keith, if the Gerity works like a Dishmaster, there is a reservoir for diluted dish washing liquid. When flow is diverted from spout to brush, it draws a small amount from the reservoir on demand to mix with the spray emitted by the brush. On a Dishmaster, there is a button on the wand to activate the soapy spray; otherwise it will spray clear water.
We had a Dishmaster that we brought along from house to house back in the '80s. They make sense when, in Dishmaster's words, you have "those few dishes" to wash, and ours did tend to eliminate the issue of dirty dishes left in the sink. Even the teenagers liked to use it. When we remodeled the kitchen at our previous home, the DM went out to the garage laundry sink where, due to lack of use, its spout eventually froze in place and wouldn't swivel anymore.