Push-ups, Plank, run, walk, bike, swim, sex.....all of those you can do it for free.
Why need gripbell for? I find it pointless.
To each its own.
When I was health I had client that was in her 80's and so was her husband. The husband was in amazing shape for guy his age, not an ouch of fat on his body and stood nice and tall. I asked him what was his secret and he told it was owning his own hardware store and having to carry bags cement all of the time. His guy could had put some kids to shame in how fit he was . Hard work will do it too.
Until I came to where you said "is a form of dumb bell or kettle bell" I expected it to be something to eat. Produce makes me think of food. I am not up on exercise equipment but it turns out to be a new product to use for an exercise routine.