You can send Bitcoin via text message so as long as you've got 3G, then game on. Don't see why this can't be done with other assets like Steem as you say.
So many developing countries use non fiat backed assets for currency such as phone cards, which are traded on the black market , hold their value and work perfectly well. Would be nice to hear your thoughts on these less mainstream items?...
Also, having Steem pegged to the USD might turn out to be an Achilles heel in the wrong market conditions.
It can be changed as and when needed.