I happened to find this news at Voxer's website. I am not related to it nor planning to enter the beta but I haven't heard any news of it so might as well let you guys know.
https://support.voxer.com/entries/23850148-Join-Our-Windows-Phone-8-Beta-Program-
https://support.voxer.com/entries/23850148-Join-Our-Windows-Phone-8-Beta-Program-