It's certainly not uncommon for backpackers to carry a rain poncho, hammock, shelter and groundsheet. The Nomad Cape is aimed at lightening their load, by combining all four pieces of gear in one unit.
Currently the subject of a Kickstarter campaign, the Nomad Cape is manufactured by French startup Trail Hoppers. At the heart of the setup is a single 425-g (15-oz) piece of DWR (durable water repellent)-coated 70-denier ripstop nylon. Laid out flat, it forms a rectangle measuring 260 by 140 cm (102 by 55 in).
When utilizing it in rain poncho mode, the wearer sticks their head up into an integrated cinch-able hood, puts their arms out through the sides, then uses an elastic belt on the included storage bag to draw the poncho in around their waist. Six button snaps along the sides of the garment help keep it from flapping open in the breeze. And importantly, it's large enough to fit over backpacks, keeping them dry along with the user.
In hammock mode, the sheet is suspended between two trees via included adjustable-length webbing straps and carabiners attached to either end. The hood gets tucked out of the way inside a zippered compartment. According to the designers, the hammock can support a maximum weight of 150 kg (331 lb).
In wind/rain shelter mode, the sheet is propped up at either end by the user's third-party trekking poles, then fastened to the ground along the sides via eight tie-outs connected to included aluminum stakes. The hammock straps, which also get staked down, serve as front and rear guy wires.
Utilizing the Nomad as a ground sheet is pretty much a simplified version of using it as a tent. It's simply laid flat, and staked down at each corner if necessary. And yes, you're right … although the Nomad does serve four functions, it can't serve them all simultaneously, so it's not necessarily going to replace all four pieces of gear.
Nonetheless, should you be interested, the full system is available for for a pledge of €99 (about US$106) – the planned retail price is €149 ($160). It's demonstrated in the following video.
Sources: Kickstarter, Trail Hoppers