The problem I suspect is that the local banking system isn’t super great, needing enough money to buy a smart phone in order to accept payment seems risky.
But does it require a bank account (which was my main concern)? Per http://www.afd.fr/en/developing-mobile-banking-madagascar only 5% of Malagasy had access to a bank account in 2014.
The question is how you move physical currency out of a payment system, if you don't have actual access to a bank. Essentially if you have "money" in any kind of non-cashable form you can't use it to buy anything. So being paid electronically in an environment where most people you interact with only accept cash/goods is essentially the same as not having money.
The ability to put money into any kind of electronic payment system is, if anything, less important than the ability to withdraw it, especially if you're in an environment that is still dominated by cash payments.