Numerous mobilephone application Developer thought to help those people out so they wont have to change their habit be safe as well.
These Application Basically turn beckground of your text message screen into a camera feed. so while walking and chatting over phone you can see whats coming on your way.
This Video can explain Batter.
For the iphone users there are few Applications such as Type n Walk, iType2go (With free Versions), Email n Walk and Text Vision. few applications even allow using twitter and facebook while walking,
Android users have Road SMA but this app is only available for Samsung Galaxy S phones.
Here's the Demo
For users with Bada OS there are App like Walk n Write, and Type n Walk
Bad news for Blackberry and Symbian phone users there are no such app built till now as per my knowledge.
Please do Let me know if there are any in comments.