Need to make a challenge with friends by total intensity minutes per given period. We all do different activity, someone is running someone is cycling and someone is swimming, but we want to compete on total intensity. I suppose it will be demanded feature among many users
Will it? I don't recall seeing anyone demanding it until now, but then of course I don't see what is requested via http://www8.garmin.com/contactUs/ideas/, and I note you were staring into the crystal ball and stated your conjecture in future tense.
I would also very much like this capability, as different friends and family members participate in a variety of activities (e.g., running, speed walking, biking, swimming, etc). I have submitted the idea to the Garmin Ideas link noted above.
You could make an Active Calories challenge instead. That is possible in Garmin Connect.
Active Calories is my preferred metric for my general activity level. I have set a weekly goal for Active Calories, and it works quite well for that purpose. It even includes calories from activities that I have logged on a Concept2 rowing machine and imported directly to Garmin Connect without having the watch in the chain.
Of course, if you are of very different weight, this challenge may be skewed, since a heavy person with the same activity level will often get more Active Calories.