Laybag, Koze, Kaisr Treeless hammock:

Not exactly ultralight, but an inflatable hammock/raft @ 1200 grams. What a neat idea: https://vimeo.com/160150388?from=outro-embed & https://en.laybag.com/collections/frontpage/products/lay-bag-green-2?variant=16884098881 US$79! PS: I see these are going for A$46 on eBay at the moment! http://www.ebay.com.au/itm/Fast-Inflatable-Air-Bag-Sofa-Travel-Camping-Beach-Lazy-Lounger-Sleeping-Bed-SHI/272248762981?_trksid=p5713.c100041.m2061&_trkparms=aid%3D333008%26algo%3DRIC.MBE%26ao%3D1%26asc%3D20140131132314%26meid%3D4a284c81e6e64d51b741c794527fcb36%26pid%3D100041%26rk%3D5%26rkt%3D34%26sd%3D172141280403

Now available Aliexpress from US$30: http://www.aliexpress.com/premium/laybag.html?ltype=wholesale&d=y&origin=y&isViewCP=y&catId=0&initiative_id=SB_20160615150200&SearchText=laybag

Update: Those ‘Laybags’ are getting ridiculously cheap. US6.79! (Sept 2018)

See also:

https://gearjunkie.com/koze-no-tree-hammock

https://www.indiegogo.com/projects/kaisr-original-the-ultimate-inflatable-air-lounge#/

Other hammock related posts:

http://www.theultralighthiker.com/a-hummingbird-in-the-hand/

http://www.theultralighthiker.com/adjustable-hammock-ridgeline/

http://www.theultralighthiker.com/continuous-loop-another-great-hammock-idea/

http://www.theultralighthiker.com/whoopie-slings-what-a-great-idea/

http://www.theultralighthiker.com/side-insulation/

http://www.theultralighthiker.com/hammock-pad-extender/

http://www.theultralighthiker.com/diy-netless-hammock/

http://www.theultralighthiker.com/klymit-hammock-pad/

http://www.theultralighthiker.com/make-your-own-tarp-or-hammock/

http://www.theultralighthiker.com/hammock-camping-double-bunking/

http://www.theultralighthiker.com/hammock-hunting-till-dark/

http://www.theultralighthiker.com/all-in-one-hammock-tent-poncho-backpack-at-1-2-kg/

http://www.theultralighthiker.com/laybag/

http://www.theultralighthiker.com/all-you-ever-need-to-know-about-tarps/

http://www.theultralighthiker.com/tier-gear-catenary-cut-hex-tarp/

http://www.theultralighthiker.com/900th-post/

http://www.theultralighthiker.com/sleeping-pad-reinvented-big-agnes-q-core-slx/

http://www.theultralighthiker.com/modifyingshortening-hiking-mats/

http://www.theultralighthiker.com/catenary-cut-tarp/

http://www.theultralighthiker.com/thermarest-speedvalve/

http://www.theultralighthiker.com/upper-yarra-track-section-seven-mushroom-rocks-carpark-to-phillack-saddle/

http://www.theultralighthiker.com/hole-less-ponchoshelter/

http://www.theultralighthiker.com/hammocks/

http://www.theultralighthiker.com/hammock-camping/

http://www.theultralighthiker.com/the-ultralight-deer-hunter/

http://www.theultralighthiker.com/hunting-in-fiordland/