I am not sure about apps, but there is already a stable coin made there called Money On Chain and it is uses to some degree in South America. I am not aware of anyone who tried to make a Drivechain-like system on Rootstock, but rule of thumb is that anything that can be done on Ethereum or eCash can be done on Rootstock. Most things that work on Ethereum can be deployed on Rootstock. I guess Mlkut Name System will soon be a thing you could try.