Can I send text messages to someone with iMessage?

I don't have an iPhone or Apple device, but my friend does. He suggested staying connected with iMessage. Will my regular SMS messages go to him as just plain texts, or will they show up in iMessage, and vice versa for me?

IMessage and SMS in the iPhone are joined together. The only difference for your friend is that he or she would have to pay for a regular SMS, and you can't message him an I message because you don't have an iDevice.