Looking for apps - 3g/4g limit and bias wi-fi

[goixiz]

Im still not sure when my 920 is within my wifi @home is it switching over and bias the wifi and not using up my LTE/4G (im only paying for 200MB).

With my android phone i can tell if its using the 3G/4G or wifi because i have a program call 3G watchdog and it will limit my monthly usage (preset).

Is there a similar watchdog app or can i make sure that it uses wi-fi and not the 4g when both is present.