I have an Actron pocket scan tool that does the basics. It reads codes and pending codes and allows me to clear the codes. You can find them on eBay for less than $50 delivered. Harbor freight has a variety of readers ranging in price from $55-$110. If you are into apps you should look into dashcommand, which works with a wireless reader plugged into the OBDII slot on your vehicle.
DashCommand - Palmer Performance Engineering, Inc.
The dash command app works with an elm327 wifi OBDII reader you can find on eBay for $20 BIN.