I have a good friend who is currently pregnant having used the shettles method. They were very strict about their timing of sex, and also about their diet. They both cut out all salt and perhaps other things well before and during ttc- I think the reasoning behind it goes that "girl" sperm survive better in a more alkaline environment (or perhaps the opposite).

Yet to see if they actually produced a girl or not, but I do know that they did more than time their ttc. It actually looked pretty tough! It also took them a bit longer to get pg than with their first, perhaps because the opportunities were more limited due to having to time the sex.