Do not worry, I won't automatically assume you're some ricer or doing illegal activities. I could care less what your intention is. You, like me, have an interest in putting a scanner in your vehicle, not to mention integrate it into your car PC, which is good enough for me, so I shall reply without some stupid and snide judgment or remark.
Anyway, there was some mention of Icom PC based scanners, meaning they make PCI hardware scanners that are meant for a PC. I don't know about Icom, but I know Winradio does make such scanners.
However, if completely scanning from the PC isn't your thing and you want the option to physically control a scanner aside from the PC, then you can try a Uniden scanner. Do you already have such a scanner? If so, then I will assume you want to use the scanner you already have instead of shelling out a few hundred dollars for a new scanner.
To answer your question, yes it is possible to control a Uniden scanner with your PC. Uniden has software called E-Scanner Plus. The software that comes WITH your scanner, just basic E-Scanner, won't suffice because it only allows you to program frequencies, not actually control it.
I will also assume you want to integrate scanner control into a front end somehow? I can't speak for other front ends, but I will assume it's possible, assuming you know how to code. Having said that, I recommend Road Runner with Digital FX. You can download the latest version of Road Runner here and the latest Digital FX (as of this post, is 3.0) from here.
However, to integrate scanner control software into Digital FX, I have been told that one needs Butel software. As far as actually integrating this software into Digital FX 3.0, I have yet to figure out that part. I know that you can open up .skin files and play around with them that way, which is really neat, but you must be careful. The scanner.skin and scanner2.skin files are what you should look at, but like I said, I haven't gotten that far yet. Maybe someone else can pick up where I left off and tell you what to do. Good luck either way.