Students should be accountable not only in station work but in gaining their education as a whole. The saying goes you can lead a horse to water but can't make it drink. Such is true with students and education, we as educators can give them to tools to be successful but it is solely up to them how successful they can become. they need to realize the more hard work and effort they put in the greater the rewards, and it tells them it is up to them and they need to be held responsible and accountable.
I really liked Thinkfinity and that you can narrow your search to exactly what you're looking for. The interactive maps and videos are great. They can draw key landscapes for a particular reagion and really see it from all angles. As far as apps go I found an awesome reference The CIA Factbook app is great, very user friendly and has a ton of information. A really useful app when it comes to writing a report or researching countries. They can use that to make a fact-card have the country on the front and "stats" of that country on the back (population, land area, currency etc.) Each student is responsible for at 3 different cards. Another app i found was The National Geographic Explorer, it is the magazine but in an interactive form, it provides movies, audio and pictures that cover everything the magazine has in it. I think it's a really interesting way to read and explore a magazine instead of just reading it. Each student will be responsible for a worksheet that goes with the certain topic researched on the app and is expected to complete it in the allowed time.