Useful job

I've been really thinking about going back to work or going back to school. The one thing that I would like to have is a job that is useful not just in America but in any country. I reflect back on my last mission trip...it was to Burundi and at the time I worked for a software company. My job was to log in to client computers databases and do work from my own computer. I can't remember how many times I tried to explain this to the Burundians who would ask what I did for a living. I think the last time I explained it, the man said to me "You know, I am 30 years old and I have never once used a computer." This was an educated man, by the way. I realized my job was nothing to these people. As important as I thought I my job was back in the US, it was of absolutely no significance or use to the Burundians during that trip. So now I am searching for something to do/study that is useful globally and of interest to me.