It's a good solution, the problem is pretty rare tho tbh... Looks a bit funny on front of rad too! I like the rapid installation tho, that's pretty good!!
In 8 years plumbing, I remember one radiator that had a sheared air vent (built in myson type) that would have benefitted from this design...
I want a similar device that can be attached to a 15 or 22 or 28 copper pipe for stubborn air locks etc, that would be a bigger target market, probs not as easy to design tho?