well ,to my existing knowledge, by islamic approach; only gold and silver can be accepted as money. in fact, I am not sure even about silver because just gold is being accepted or calculated as entity to be responsible for something.you may consider to think that bancnotes, credit card's credits , bank accounts' amount were money
but as the definition is changing to one by one and by other entities,
what is the measurement of wealth?
I think here, we may have to wait for some time, somethings will be more complicated in near future, however, I am hopeful to expect the clearer air/environment.
cheers