Hey, I can do this for it, it's fairly straight forward.
A call would be made to the coinbase API to identify your current balance, this would then be turned into a percentage and passed to a HTML5 progress bar.
I can mock up an example this evening if you prefer, but as I only have access to a BlockChain wallet at the minute a mock up would use their API (switching shouldnt be too difficult!)
The underlying code would be PHP.
At no point would I need your API key, I will pass you the code and you can add that yourself.