Although it kind of looks like a bottom, the new airbag design is purely about protecting the occupant's vitals - that'd be the head and neck area - whilst relieving the rib-cage of undue pressure during the instant of deployment.
During a crash, the top half of the occupants body will normally be thrown forward more than the lower torso, this means most airbags overcompensate for the space in between the lower chest and stomach area by trying to 'catch' the lower body even though it's either already there or hasn't moved quite enough, causing the airbag to put excess pressure on the rib cage area.
The system will also introduce an airbag 'venting' technology. This takes into account the seating position of the driver and passenger which is then conveyed to the airbag sensors and computer, resulting in reduced or increased airbag pressure according to the driver's height. A taller person requires more pressure to 'catch' because of whiplash trajectory, whilst a shorter person requires lower pressure due to lesser trajectory.
Ford says the new airbag system will be standard equipment on all 2012 Ford Focus models and eventually offered in other vehicles in the Ford range.