Google is expanding its pool of Explorers, slowly but surely. First it was people attending I/O; then friends of existing Explorers; now it's subscribers to Play Music All Access. To celebrate the release of Play Music on Glass (albeit a little belatedly), the tech giant is offering subscribers to its streaming service a chance to buy the fledgling wearable. Emails apparently started going out this morning (though, no Engadget editors have received theirs yet) inviting those eligible to request a place in the Explorer program. Of course, entry to the exclusive club still costs $1,500. Though, we're sure you'll been looking for something frivolous to spend your tax return on in a couple of months.