[gTen]

You are not limited to 4 digits, you have up to 16 characters. And the encryption on Android has not been cracked by researches. All they did was brute force it because people used short/simple passwords. If you use a full sized 16 character complex password they won't be able to break it with brute force for 10 years.

What in specific do you wish to encrypt? Like there are apps like touchdown which encrypt all your exchange/activesync stuff for example.