Price is currently membership costs MXN 1,372.00 Mexican pesos (roughly USD $104 Jan 17 2014). This seems to be somewhat Beta, with kiosks at:
MEX: T1 and T2
CUN: T2 and T3
SJD: T3 and T4
Link to page "How it works" for instructions (English version).
For foreigners, kiosks will provide the immigration form ensuring their legal status in the country.
It is unclear what this means, as US Citizens visiting Mexico are normally required to fill out two forms, Form FMM ("Tourist Card") and Mexican Customs form - as mentioned in this FT thread:
Requirements for visiting Mexico as a tourist (FMM, "tourist card", visa etc.).