Originally the T4i was listed as a compatible model on Canon's website, however at some point they removed it. An updated list can be found in the Help/FAQ/Equipment report in the software (click on 'Other Equipment To Consider Prior To Race Day'). I will include the list below too.
I have the newest SDK on my computer and I tried to simply replace the old SDK with the new one but I could never get my camera to work with it. So unfortunately it doesn't appear to be a quick change like I was hoping it would be. I don't have a T4i or a T5 that I can test with (a couple of customer have offered to ship theirs to me thankfully) so those cameras may have worked with the new SDK, however I want to make sure the new SDK can still work with the older model cameras since that is what most people have. One day soon I'll block off 6 - 10 hours to dig through the documentation and get it to work for the older models and the newer models.
This weekend I'll push a new update out and explain the improvements I've made with the RunSignUp interface and with using more than one Results Kiosk connected to the main timing laptop with a wireless connection. I'll see if I can take another quick look at the new SDK before pushing the update out, hopefully I'll find that I overlooked something small that will get it to work with new and old Canon models. Tomorrow I'm travelling with one of my timing crews to Texarkana to time the Run The Line Half Marathon (race is on Sunday). So I'll be riding in a car for 5 hours and hopefully I'll have a few hours tomorrow night in the hotel where I can look at it.
At the Run The Line race this weekend we'll have split zones on the course, the wireless results kiosks, an announcer system showing names of participants well before they reach the finish line, Chip Start (possibly with wave starts), and of course we'll be timing more than one race at a time. We'll record the finish line with the new Polaroid XS100 that we bought and of course provide results on RunSignUp with a video link for each participant. So this will be a full setup of everything we offer. Next weekend I'll be in Mountain View Arkansas timing the Sylamore 25K/50K race. In March, 5 of the events that we'll be timing have between 500 and 2,000 participants and of course April and May are will be busy as well. Going to all of the bigger races that we time is of course the best way for me to discover ways to improve the software. Of course I plan on going through the Feature Request and Bug Report threads and working on anything I can find in there too that is outstanding. I'll keep everyone informed on when updates are available and what is included in the update. Here is the camera list:
EOS-1D Mark III
EOS 40D
EOS-1Ds Mark III
EOS 450D/Rebel XSi
EOS 1000D/Rebel XS
EOS 5D Mark II
EOS 50D
EOS 500D/Rebel T1i
EOS 7D
EOS-1D Mark IV
EOS 550D/Rebel T2i
EOS 60D
EOS Rebel T3
EOS Rebel T3i
EOS 5D Mark III
EOS-1D X
<EDIT: 11/11/2016>
The newest SDK has been implemented. The software now works with the following models: