Depending on the type of phone you have, you can get the chat apps on them now anyway. I usually run vent/mumble on one of my other PCs because my FFXIV PC is for that game only and nothing else. I looked into getting the app on the tablet as well, but I'm unsure as to it's reliability. I don't really see ps3 users having an issue because they can simply just use their laptops to voice chat.
Not everyone playing on a PS3 has a spare laptop lying around. I would like to have some sort of voice chat available for PS3, but I think way back when, Tanaka said it just couldn't be done. Of course that was three years ago. A mobile app would be very nice though. I think you could hit way more people with a smart phone they could dedicate than a lap top. Short of that, I think an integrated keyboard/controller like I used to have would be really nice. I know Sony makes a mini-pad that you can clip on to a standard controller, but I don't know if that would really have all the functionality you would need.