I keep a hand written notebook.
Warning!! Handling a Hasselblad can be harmful to your financial well being!
Nothing beats a great piece of glass!
I leave the digital work for the urologists and proctologists.
I never see film in stores either, so despite being on my third iPhone, and having an iPad and two Macs, I use post-it notes on the fridge to keep track of what's in the freezer.
flickr stream - http://www.flickr.com/photos/ewf_photography/
I don't have a smartphone, I just have a whiteboard on the side of my film freezer and some whiteboard pens so I can add or subtract the film as I use or buy it .
I use an Excel spreadsheet, but that means I never have it with me when I need it.
I need to put my inventory into Evernote, which I can get to easily from my phone, home or work computers.
My other camera is a Pentax