Just as an update to my post above.
Came across this yesterday for entirely different reasons. something called a Helikite http://www.allsopp.co.uk/
A cross between a balloon and a kite. Used in professional circles, including the military for hoisting things aloft.
2 things of note. First is that normal balloons tend to get forced down towards the surface in a high wind - which is what will happen to the rescue me balloon. So detracts from its utility as a visual signal. The Helikite does the opposite due the nature of its design.
The Helikite has a maximum wind speed limit of 35 mph. Which is probably well in excess of the Rescue Me Ballon's capability. And still not good enough for the British hills and Moorland on a bad day.
Nice idea Rescue Me Ballon chaps but fraught with impracticalities. That severely limit its functionality to all but a nice Californian sunny day.