If your ROM version is less than 4.2, your phone works just fine with most Garmin devices. If you plan to connect an ANT+ forerunner (310xt, 610, 910xt, 405, 405cx, 410) you need an OTG adapter, so that you can plug in the Garmin USB ANT+ dongle. Just follow the instructions here or here.
If your ROM version is 4.2.x, you may have troubles. That version basically breaks the USB, and if you connect an old Forerunner 305 you'll get a security warning when you run my app; if you connect an ANT+ key, you'll get a security warning about the dynastream driver, and you'll probably never get to step 3 in the instructions above. Unfortunately, it's not something that can be fixed by an app. You have to wait for version 4.3.