Development topic: http://gtaforums.com/topic/467104-

Introduction:
Vice City Radar Zoom is a modification for Grand Theft Auto: Vice City utilizing the CLEO Library. It simulates a feature from GTA IV that allows you to fully zoom out the radar and to force the display of the area and vehicle names with the press of a key. Hold the "T" key to enable this behavior and release the key to revert back to the original behavior. You can modify what key to press by editing SEZoom.dat, a plain text file, and changing the hexadecimal number to any virtual-key code.

Installation:
* Download the mod (click the Download Mod button). If you are unable to open VCRadarZoom.rar, rename the file to VCRadarZoom.zip.
* Download CLEO for Vice City at http://cleo.li/.
* From the CLEO download, copy VC.CLEO.asi into Vice City's folder.
* If CLEO.asi already exists in the folder, you must delete that file.
* From this mod download, place the CLEO folder containing SEZoom.cs and SEZoom.dat into Vice City's folder.
This mod has been tested only on VC v.1.00 US.

Video:

San Andreas:
Check out Silent's version for San Andreas here.