Handcent and ChompSMS have what is called a blacklist feature. It won't lock down your entire message application but you can set your messages to Blacklist and when you want to hand over your phone you can select "Hide Blacklist" which will hide all messages that have been added to the Blacklist. You can also set up a password so that if you want to show those Blacklist messages you have to input a password to show them.
You don't have to Blacklist all threads, you can pick and choose which contacts/threads you want to Blacklist(hide). I didn't check to see if you can Blacklist one message in a thread or not, but you could always try that out if this is an option you would like to take.
As for blocking the entire app, I am unsure if that's actually possible. Did you check the market for an app like that?
BTW, Handcent and ChompSMS are free apps.
Handcent and ChompSMS have what is called a blacklist feature. It won't lock down your entire message application but you can set your messages to Blacklist and when you want to hand over your phone you can select "Hide Blacklist" which will hide all messages that have been added to the Blacklist. You can also set up a password so that if you want to show those Blacklist messages you have to input a password to show them.
You don't have to Blacklist all threads, you can pick and choose which contacts/threads you want to Blacklist(hide). I didn't check to see if you can Blacklist one message in a thread or not, but you could always try that out if this is an option you would like to take.
As for blocking the entire app, I am unsure if that's actually possible. Did you check the market for an app like that?
BTW, Handcent and ChompSMS are free apps.
I think he was talking about locking the application so noone else can look at them when they have his phone. If that's the case, then i don't know of a single app that can lock certain apps.