I have multiple employees I need to send reminders, notices to en masse. Sometimes I will want to group these employees into categories and only send to those select categories. I thought ZC would be a nice way to add their info or allow them even to edit their own info. My employees tend to have mobile companies like Simple Mobile, Boost, MetroPCS... ideally I would prefer a service that doesn't require knowing the mobile provider.

I know several SMS services work with ZC - do you have any suggestion?