Study Bibles and Daily Devotionals

I'm working on a new book proposal right now -- actually I have several ideas bouncing around in my head, but I thought I'd get some input from all of you. So, here's my question:

What kind of materials do you find helpful in study Bibles and daily devotionals?

I'm working on an idea that might combine the two -- a study Bible that is also your daily devotional. If you were to use something like that, what topics and information would you like to see covered?