It seems most of the decisions in life are made in favor of the present you, or the future you. I wish the future me could sit beside the present me, and discuss how I was going about my day. Instead, it's a rather one-sided conversation. There are obvious choices, like food, spending money vs. saving, going to bed early - these are all clear calls, and would be even more clear if the future me was here to advocate on his behalf.
There are subtle choices, too. Things like how to engage in relationships with others, how to invest in myself and others. These would benefit the most from a pocket-sized future me.
If anyone invents this, I'll buy.