How can I send Bitcoins via SMS? I am considering working on giving Africans access to trade using Bitcoins. 

In many ways, parts of Africa is more developed when it comes to mobile payments than the west. The success of M-PESA confirms this. Their security is based upon a special SIM card (see Step 1 in this getting-started guide).

My question

Would it be possible to set up a service where one could send and receive Bitcoins securely via SMS? An additional condition to this question is that the SMS could be sent from a good old crowbar mobile phone without any access to a computer to perform encryption. One should also notice that postal services in these countries should be considered insecure.

Motivation

My motivation for this project is the heavy costs involved with making an overseas transaction to an individual in Kenya, because M-PESA only accepts transactions from oversees using Western Union. This is important because I know that there are huge flows of money going from Africans (and more so Asians) in Western countries to their family-members at home.

Additional points

It should be noted that one can send SMS for free amongst others to Kenya via Google SMS. Their only condition is that the receiver responds to the SMS occasionally in order to avoid it getting used for spam.

Currencies in some African countries are very unstable (for example in Zimbabwe), so the Bitcoin currency could maybe be considered a "hard currency" compared to the local ones.
Just an account on http://phoneco.in/  because thats exactly what the service does.  [Update: Phoneco.in is defunct.]

Update: A new service as well to check out. http://dialcoin.com/ [DialCoin's site is up yet but has suspending service.]