Ditto is an iPhone app reminiscent of Foursquare, but instead of announcing a check-in now, the app lets you tell your friends what you plan to do - then they get to counsel you on how you should do it.
The buttons for various activities let you choose "Eat out", "Work", "At home", etc. Afterwards, Ditto friends can give you suggestions to flesh out the details of your plan, like where you should eat in the area. Or if you've spotted another friend's awesome-sounding plan, just jab at the "ditto" button. Ditto also lets you do traditional check-ins, which you can push to the platform of your choosing (Foursquare, Twitter or Facebook). Free at the App Store. [iTunes via TechCrunch]