The UTEC is offered by TurboXS.com (and maybe others, I'm not sure) and is a very powerful tool. It's not as pretty as the Apex setups, but it is a lot more powerful. Has great knock correction and very high resolution. It can control boost (open or closed loop), timing and fuel mixtures. Maps are easy to tune by adjusting each cell or by downloading new maps and loading them yourselves. Since the stock ECU is still in place, it is still very safe and good for daily driving.
You interface with the computer by connecting via a serial cable. Doing the tuning via an empeg would be hard to do, but displaying info from the "Digital Dash" would allow you to use your empeg as a full out gauge replacement.
I believe it can store up to 7 maps within the computer itself. So you can have one for race gas, one for pump gas, one for valet parking, one for a stock setup, etc etc.
Here is a link to the WRX Hackers forum for the UTEC:
http://www.wrxhackers.com/modules.php?name=Forums&file=viewforum&f=1
And info on the product itself:
http://www.turboxs.com/UTEC.htm
I'm still learning about this myself, but I know several people that are using this so I can get info pretty easy.