WTB 3g Phone GSM (ATT/TMobile)

I am looking for a 3g Phone to send to PI for my 2 daughters, I haven't been able to keep up with their growth I just want to see them when I talk to them, with all apps (SKYPE, TANGO, Viber etc.) available for 3g phones now that will become reality, and you can make it happen, let me know what you have, preferred Iphone (hey my daughters are teenagers) but android and compatible are acceptable..THanks much!!!!!!