See the Python section of the Selenium RC documentation:
http://seleniumhq.org/docs/05_selenium_rc.html#python
You may be able to run Selenium tests from Jython. In that case, you can simply integrate Selenium scripts into your Sikuli scripts.
Try the following in the Sikuli IDE. You may need to modify the import statements to point to specific files in the Selenium project.
from selenium import selenium # this will probably need tweaking...
slm = selenium("localhost", 4444, "*firefox", "http://www.google.com/")
slm.start()
# etc...
This guy appears to have had success controlling Selenium from Jython: http://adam.goucher.ca/?p=367
My conclusion: it will probably be easiest to stay in Jython and control Selenium from there. You could integrate both tools into a single script.