Does any exist already ?
Tether has historically been a good peg to the dollar but it's value comes from a centralized company that buys and sells tether to maintain the price. If the company fails, you lose everything.
The only safe option is bitUSD which is a decentralized peg to the dollar. It is an amazing system done by decentralized price feeds and a smart contract that can be settled on the blockchain. Check out
BitShares.org/wallet/
There is also bitCNY, bitGOLD, bitSILVER, even bitBTC which will always be worth at least its face value and sometimes slightly more.