There's a free version of this, but I use it every night no matter where I'm sleeping (home, my parents', Paris, Lisbon, Belize, Barbados....) so I "splurged" for the full version.
I can't believe what a difference it makes in my sleep!
The Twitter app has improved, but I love Echofon for searching and creating lists.
This is the "OMG soon we won't need wallets" app.
So convenient and easy to use!
What are your favourite apps??