There is an alternative. At Monetran, we've designed a token for use on the Stellar network which uses a novel approach to achieve stability.
Instead of backing the currency with gold or other commodities which can't provide stability of price, we have backed our crypto with interest bearing financial assets, i.e. short term T-bills.
Although USD backed coins can provide stability in the short run, it comes at a cost of built in monetary inflation. If held for any significant amount of time, the purchasing power of the coin will decrease.
https://www.monetran.com/ Backing with T Bills is a good idea, What Form will the T Bills come in?
T bills are only guaranteed in nominal amounts, and if there is inflation in the economy the return on principal becomes less than the original Investment. So calling it totally stable is not entirely being honest.
The form of the collateral is 3 month T-bills. Loss of principal is not a concern.