I've got the Innova 3100 that I purchased a long long time ago. I've used it to reset the gas cap/vacuum leak code the 4runner was throwing when I was in the process of searching for a locking gas cap.
I don't have experience with other OBD2 tools to compare it to, but the Innova has all the general functions and it tells me the code when my check-engine light turns on, and allows the code to be cleared. There are lots of OBD2 readers on the market nowadays and most are very affordable (and even more so when on-sale). Don't spend an extreme amount of money for one - I find I've used mine just a handful of times. A basic unit that will read/display the code, and allow for manual clearing of the code should suffice.