Great idea, why not make something relatively safe like say i dunno..........benching with no collars and just letting plates slide off when you fail and make it really dangerous by attaching a heap of point loaded weight to the bottom of the average Australian truss roof home, last time I checked bottom chords a solid 3.5cm of softwood pine.....of course there is 7cm of fat in the vertical profile but you are putting a stress point in there when you drill a hole to attach the spotter of death.
The whole premise of a truss is it works as a whole so you can use small and economical members. However if a critical component like the bottom cord fails catastrophically by I dunno.....maybe bugee jumping a large static load of wight by rope off it. If that happenend there is a fair to average chance you would not only have your weights crush you but they would be followed by a heap of timber and roof tiles/iron.
If you are one of the 1:1000 Australians who lives in a skillion roof home constructed in the purlin and strut style OR you work out in the garage under the house then yes this superb engineering masterpiece would be an ok investment