Update on 3100:
Love USB port. All I use is 8GB USB drive for my music. I've movie in CD/DVD slot for those long waits @ train crossing or carwash or just front passenger entertainment. As for camera: I've no desire of installing one. It usually takes a second or two to start up for most models - I rather use those huge side mirrors that Toyota gave to 4R. Pioneer makes 5100 with motorised large screen, but be aware it won't sit flush with your trim because it needs clearance to tilt.
This one in F150 from YouTube, but it'll give you preview of the unit:
<object width="660" height="525"><param name="movie" value="http://www.youtube.com/v/g43CnZTVlms&hl=en&fs=1&color1=0xe1600f&color2=0xfebd01&border=1"></param><param name="allowFullScreen" value="true"></param><param name="allowscriptaccess" value="always"></param><embed src="http://www.youtube.com/v/g43CnZTVlms&hl=en&fs=1&color1=0xe1600f&color2=0xfebd01&border=1" type="application/x-shockwave-flash" allowscriptaccess="always" allowfullscreen="true" width="660" height="525"></embed></object>