To avoid having anyone discover information from your phone, don't use it for these sort of functions. If you don't use the Internet browser, or GPS, on your phone, then there's little for them to see on the phone.
If you can remember telephone numbers, then you won't need to store those on the phone either, but remember, the moment you call someone, or use an Internet browser (even if you immediately clear the history, cache etc), you've transmitted this information over the air, and with the appropriate level of technology and/or access to the network, that information can be retrieved without requiring any physical access to your phone.
I've got an Ironkey USB drive now, that is cryptographically secure in hardware. If the wrong password is used too many times, it will physically self destruct, supposedly rendering itself unusable (expensively secure, it's an £80 4GByte USB drive!) I can think of mechanisms that could be used to access the data, but they're complex, expensive, and difficult, so unless I'm clearly the mastermind of some vast terrorist conspiracy, then anything I store on there is probably safe from anyone accessing it.
Of course, RIPA would allow me to be jailed for refusing to provide the password to it, but they certainly can't trivially gain access to the data.