This term originated from a TV advert in september/october 2009, where a teacher takes a phone off a pupil and then says the legendary line... wicked phone.
This has come a common phrase in many south east towns. The way you say wicked phone is very important and to imitate the advert is crutial in getting it correct.
You need to emphesise and elongate the i in wicked more than you normally would.
It can be used when something is really good and you want to express how good it is.
Man 1 "i just got an A in my Maths A-level"
Man 2 "ahh wicked phone! well done!"
Man 1 "I nailed Suzie last nite!"
Man 2 "wicked phone, she has massive tits!!"
Man 1 "have you seen my new phone?"
Man 2 "Thats a wicked phone"