The 'inventive' Japanese who brought you the web-connected tea kettle in 2005, have something to offer for fall detection and prevention beyond motion sensors. A Japanese company has invented an airbag that inflates in 0.1 of a second if it detects a person falling backwards. Designed for individuals with epilepsy who are at risk for falls, the product will also be targeted to the Japanese elderly, where 22% of the population is over the age of 65 (compared to 12% in the US).
Problem # 1 -- only useful for backwards falls.
Problem # 2 through n: After you study the picture, I think you will agree that as a product your aging parent or grandparent will strap on in addition to their clothes, it's a bust -- so to speak.
So right now, it's humerous (as well as unavailable).
However, like all early ideas, maybe the concept will evolve into something that would be useful someday -- a wearable and tiny airbag.