One quick question - Has anyone ever used 'Maybe Baby'? (the little saliva test to check when you ovulate)

A friend of mine has got one and was telling me about it the other day, and I was wondering what peoples thoughts were, if anyones used one, and if they think it would be a good investment. (she said about $70).

I'm considering it, but want some opinions/advise first.

Thanks,

Shan