Agreed. I doubt each individual sensor needs to transfer more than a few bytes each time and probably not more often than a few times a second (and thats the ex

Agreed. I doubt each individual sensor needs to transfer more than a few bytes each time and probably not more often than a few times a second (and thats the extreme case - like you said, once a minute is more likely). This can easily be done with a low cost, low power RF circuit (and low power would have some additional advantages over the design in the article - eg, smaller batteries = smaller device) and wifi connectivity can still be achieved through a hub/base station. You only really need one wifi connection per sensor installation. If you need special super sensors that have their own connection for some reason, then special case those, charge appropriately and leave the base sensors as cheap sub-$10 devices. A simple temperature or vibration sensor or whatever shouldn't need to cost much more than about $5 or so, nor would I be willing to pay all that much more than that (certainly no more than $12).