I just added a gallon of pureed peaches straight into the primary of a wheat that wasn't coming out quite according to plan. Blanched them quickly to make them easier to peel, then sliced them up and threw them in the blender with a little tap water until they were about the consitency of a smoothie. Repeated the process until I had a gallon ice cream bucket full, then just sanitized my funnel and dumped straight into the primary. Don't know the results yet, but it's been a week and I see no signs of infection in the fermenter.
A few years back I did a spiced apple ale that called for a gallon of unpasteurized cider to be added to the primary. Again, I didn't boil or sterilize the cider in any way. That came out amazing!