Rosamond and Yeadon at Loughborough University, U.K. created this …
… study was carried out to design, construct and assess a training aid to assist in the learning of a backward handspring. …
Though they consulted many expert coaches, I doubt any of those experts would ever use this machine.
To see how it worked, download that 2009 research study – The biomechanical design of a training aid for a backward handspring in gymnastics (PDF)
Gymnastics Coaching.com 