The backing would be done through bullionvault. Or I could use bitcoin as a backing with the wallet being public and viewable.

I have thought about inflation of the price going over the asset value. It would be similar to a stock/share/company bond though with a positive net asset value.

For example:

The Company Bond starts with a value of £100. Market is good and news is positive for the company. The bond now trades for £150 but still only has a value of £100. However can also go in reverse market is in decline and bond now trades for £70 but still has a value of £100 when it matures and is cashed back in with the company.

It's just an idea at the moment and any thoughts are greatly appreciated be they positive or negative.