Adding the equivalent of an 8x zoom lens to a phone is probably a pretty futile thing to do if you're expecting high-end results, but the novelty value alone is probably worth the ¥8,800 (£43) the thing costs.
As you'd expect at that price, there's more than a couple of bits of glass and plastic involved. Focusing comes courtesy of a ring on the barrel of the lens and Greenhouse has also included a tripod.
The tripod both holds the whole rig steady and the lens in place against the body of the phone, which makes some kind of sense. Naturally, this is only available in Japan at the moment, but small quantities of grey-market exports are likely.