Only for the SonosNet network, not a ‘normal’ Wi-Fi network. 

Great, that’s what I was hoping for . . .

Any Sonos speaker will do the same thing, too, assuming it can use SonosNet. They all reinforce/repeat the SonosNet mesh network. So you could just as easily drop a PLAY:1 in that location. More expensive, sure, but you get the benefit of having an extra speaker there…

Note that, unless there are Sonos players which are struggling to maintain a wireless connection, plonking a wireless Boost down as a SonosNet extender could be a waste of time. SonosNet will try to minimise the ‘cost’ (i.e. number of wireless hops) back to the wired network. Often as not it will end up ignoring a Boost if the player connections are otherwise ‘good enough’. 

Visiting http://IP_of_a_player:1400/support/review and clicking on Network Matrix would reveal the state of things, before and after installing a standalone Boost.