Hi Matt - I didn't mean that an app actually replace the 'binder' as to the point you made - you still need somewhere to store your negatives. What I meant was (and this is more a question than a statement) is that an app like MDC replaces the need for binders full of development specs for the film I'm using ... I think. That and it becomes a really simple and accurate way for a newb like me to keep track of development times, agitation cycles, etc. That was really the nature of my inquiry.
I think I know what you are thinking.
My concern isn't with the apps themselves, with one big exception, it is with the quality of the information built into them.
The big exception is that I really don't want an expensive battery powered item like an iPhone to get anywhere near my processing area.
A customizable process timer that allows you to record the steps of your process and play them back at will is otherwise a great idea.
But I think that you need to decide on the details of that process before you record it. Or at the very least, you need to know the source of the recommendations built into the app.
For fun, I did some looking around for apps that are functional on my cheap Android tablet. I located this interesting option from an entity referred to as "Darkroom Solutions":
http://darkroom-solutions.com/#home
It offers three things I like:
1) there is a trial version, so I can see how it works before I pay for it;
2) there is an explicit notation stating that all recommended times are based explicitly on manufacturers' recommendations. As an example, when I tried Kodak T-Max 400 in HC-110, it actually referenced the appropriate Kodak data sheet by number; and
3) it is fully customizable.
What I don't like is that there is no way to export customized settings, or to even print them out. So if I want a backup, in case my tablet goes away and Darkroom Solutions cannot help, I would be out of luck.