I've been using Message Delay Express for a while. Besides scheduling the text to be sent later, it also allows the text to be repeated at certain intervals, so you can keep repeating the same text every month when you know she's ovulating.
Check out my thread Essential android tools for modern players and alphas to find out how to make your android phone your wingman, or click here and scroll down if you only need to root it.
Want sound that puts iPods and iPhones to shame? I got you covered!