no they don't have that feature. i suggest keeping your plug and play unit and removing the built in unit and sell it. i have my unit plugged into my headunit along with my ipod. if you are running a stock headunit i would strongly advise you to upgrade to a new one, right not crutchfield has a very nice unit for an extremely low price. here is the link for it.
p.s. because of their price being lower than ones on ebay, i just ordered 6 from crutchfield and plan on selling them on ebay for t he same as all the others on ebay, that how good of a deal it is.