Trulia has a built in crime map which you can use to see how crime varies block to block, neighborhood to neighborhood.
Here is our Crime Map for the 77099 zip code you were asking about: http://www.trulia.com/real_estate/77099-Houston/crime/
But you can also see this at a finer level, by going back to the property page, scrolling down to the Local Info section, and clicking the "Crime" tab above the map.
Good luck with your search!
Community Manager, Trulia Voices
The most reliable source for crime activity in a particular area is your local police department.
For your information, you can check the address listed on http://www.crimereports.com. This site will give you a recent list of criminal activity for a particular address, zip code, city, etc. Again, the most accurate source is always your local police department.
Please let me know if I can be of further assistance.