I've been using Little Snitch for years now, and ran across GlassWire while casting about for alternatives. I'd be very interested in switching to GlassWire for Mac (whatever you end up calling it, though that sounds just fine to me) if it will provide the same sort of control over outgoing connections as the Windows version.
I think one key to making a successful product is having a reasonably up-to-date set of default rules in place. The fact that Little Snitch is a bit slow in this area is the reason I started looking around for alternatives: I just tried installing the latest version of LS on a new computer running El Capitan, and was immediately forced to deal with a spate of notifications about connection attempts unfamiliar processes ... all of which appear to be part of the default OS installation. That sort of thing can be frustrating even to an experienced user. I imagine most new users would probably uninstall the product immediately.
I'm sure it must take a lot of work to keep the rules updated and documented, so users will know what's getting through and have the information they need to make decisisons about what to change. But it's important to keep the initial setup as hassle-free as possible, so new users will have some time to get used to a product before being forced to make a lot of decisions.
I'm looking forward to checking out Glasswire for Mac when it's ready.