I'd rather not throw in arbitrary classes without thinking about the design for handling HTTP requests. For example, do we want an HTTP request class that has a isMobile() method? How about something like https://github.com/serbanghita/Mobile-Detect

Overall, I'd rather see this developed as a plugin and we identify the pain points along the way and fix them in core. Eventually, we pull this whole thing into core. Otherwise, I fear we end up with a partial implementation that we either ship (not again!) or strip out before the 1.9 release.