[dmurray]

MPesa doesn't store your money in some kind of private currency with a fluctuating value. If you're thinking of it as storing "minutes" as some American cellphone providers would, that's not right.

You deposit and withdraw Kenyan Shillings, or your local equivalent, just as if it were a shilling-denominated bank account.

[Grustaf]

Yes, and you could make this hypothetical Kenyan cryptocurrency work the same way. One KCoin is one shilling, redeemable for minutes.