Typing on a smartphone is tedious. Special characters are the hardest; lowercase letters are generally the easiest. But even a long all-letter passphrase like "correct horse battery staple" is difficult to type on a smartphone.
I normally use LastPass on my computers, and let it generate long passwords with a mix of letters, numbers, and symbols. For example: "5&8fjmYyb4^Vd2n". Since I never have to read or type these passwords, they can be anything.
There is a LastPass app for just about every platform out there (cool). The one for Android is basically a web browser. If I want to log in to, say, http://amazon.com, it can fill in my credentials. But Amazon also has a few apps: Kindle, MP3 Cloud player, App Store, etc. These apps have their own login screens.
To run the Amazon Kindle PC software, I can use LastPass to copy my Amazon password to the clipboard, then paste in to the Kindle software login screen. However, copy/paste and switching between apps on Android is clumsy. It's better than typing "5&8fjmYyb4^Vd2n" but it still is a pain.
Two other obvious examples are the Twitter and Facebook apps. There are many more.
My phone has a slide-out keyboard, so digits and lowercase letters are easily accessible. Uppercase and some symbols (those on the numbers) are harder to get to. Other symbols are very difficult, as you have to navigate UI to look for them.
Similarly, the Kindle has a keyboard and a web browser. Both are hard to use, but sometimes they're just the ticket. There is no LastPass app for Kindle.
Ideally, I'd like a way to come up with strong, easy-to-remember passwords that are also easy to type on these hard-to-use devices.