I don't know about 'best', but I do know that Indonesia has huge potential in mobile monetisation. Transactions take place with low value banknotes (1000 Rupiah most typically), which are kept in in physical form. Although consumer confidence is high in Indonesia, and the economy is rapidly growing, the pool of available capital is constrained for this reason. As one of the largest countries in the world, any increase in use of monetary services here has the possibility to lift a great number of people into the global middle class. Given that mobile penetration is high, but use of monetary services is low, the potential is certainly there.