phone-based CRM software/best-practices

[Michael Herr]

Curious if others have tips/tricks for keeping track of interested parties while filling vacancies. 
When I'm at home in my office. I log people responding to my ads into a spreadsheet. 
While I'm at work/on the go, I'm not as organized.
It's especially confusing when they contact me through multiple methods: email followed by phonecall etc. 
I also have several vacancies at the moment and have never had more than one at a time before. 

I've debated getting one of those mounts in my truck for a laptop like cops and some contractors have.

Any good apps for this purpose? Other systems? 
My best system right now is scribbled notes on paper: far from ideal. 

Many days I leave the house at 5am. Between exercise, day-job and family commitments, I normally can't get to my home office until 8pm.