I have a H7 sensor and it's working good with stock 4.3. Remember, you must pair the sensor in the app and not on bluetooth settings. There are only a few apps working at this moment like Runtastic Pro, Polar Beat (you can find the apk here on xda because it's just for S4 but is working without problems on S3), Sportstrackerlive and others.
I upload the polar beat apk here for you
Just one more thing, sometimes the H7 or H6 goes crazy and stuck so you cant pair, in this case remove the battery and conect the sensor to the stripe (without battery) for 10 seconds, this will completely discharge the sensor (this process is decribed on polar forums).