Sooo.... has anyone used a harness for their toddler??

Bumpto3 have a backpack buddy harness which I am seriously considering ordering for Aidyn. (it is comprised of a cute monkey/puppy backpack that is worn on the back and clipped up at the front, with a strap (tail) that runs from the backback to my hand/wrist)
When my next uni semester starts, there will be one day a week where I have to catch a bus with Aidyn and walk for 10 mins in the CBD to DP's work to meet him.
Our little portable stroller is just too little & uncomfortable for Aidyn now, but there is no way I can take him anywhere if there is the risk he will tantrum and refuse to hold hands with me. Especially if we are in the city.

So has anyone used one and found them to be useful?

TBH I would much rather be overly cautious by using one, than risk my little boy getting seperated from me...

Also, I would be interested to hear if anyone has seen these for sale at the shops somewhere?