Ok so for starters you will need a program called iBackupBot on your computer
Here is the link: http://www.icopybot.com/itunes-backup-manager.htm
So this mod will change signal bars and/or Wifi bars to a numeric value
For cell signal this value will range from -47 (the best service) to -130 (the worst service), The actual bar value for bars will vary from carrier to carrier.
For Wifi it will range from 0 (perfect connection) to -100 (weak as possible)
Step 1: Back up your phone to your computer (if you use iCloud then just turn of iCloud backup and sync)
Step 2: Open iBackupBot and find your backup (there may be a lot)
Step 3: Find the file called Library/Preferences/com.apple.springboard.plist
Step 4: open the file
Step 5: Look at the image below, for numeric signal add the SBShowGSMRSSI line with the true value and for Wifi add the SBShowRSSI line and the true value
Step 6: Save the file
Step 7: Press the little iPhone with an arrow in iBackupBot to restore your phnoe from a back up
Step 8: Enjoy!
To switch between the analog bars and the numeric values just tap them!
Here is my iPhone 4S on iOS 6: