The idea was fairly simple: Schemer acted as a digital bucket list, so you could plan what you wanted to do, and Google could serve you Google Offers based on your list. Seems like a good idea all around. The only real problem with the app was that Google sort of left it up to the will of the people, and didn't bother curating the activities at all. That meant that if you wanted to add "Go to Japan" to your Schemer to-do list, there would be dozens of listings for essentially the same thing, instead of one canonical item, which led to a lesser experience.
You can still download your list of schemes until February 7th, but it seems like this may not be the end for the app. Google has been suggesting users install the Field Trip app. Field Trip already suggests other places to visit and sends promotions based on the places you've seen and liked, so it wouldn't be much of a leap to integrate Schemer if Google wants.