I just want to build something that my mobile users can install on their phone, to alert them when they have a new Private Message. I really just want it to be an icon where a number pops up when they get a message.

Question 1: am I correct that this requires them to install a widget?

Question 2: if so, can you guys point me in the right direction of building a widget like this? I need it to be compatible with both iPhone and Android, of course.

Question 3: this will obviously require the user to be logged in to the site, which would require either a persistent cookie, or something unique on their phone to verify their identity. Since I'm new to this, I don't know... is that an issue for mobile widgets? If so, how do I get around it?