I always worry about Spike getting too cold. Heating my place can be a nightmare and I can't really leave the house with the heating on all day - not to mention the cost. With a tank you can get those reptile heating pads and put them under one side but this is the first time I've seen something that can potentially be used for a barred cage. It's not going to warm up the whole cage by any means but should provide a 'warm spot' for a hamster to go to when the temprature drops, particularly if you place a cardboard box over it for a hamster to make a nice nest around it. I'm sure a hamster will quickly learn that there is a warm place they can go to when it gets super cold. While pricey I think if it works well then it saves you money in the long run with heating.
If you go to the bottom of this amazon review page you can see a really cute video of a bird snuggling up to it:
clicky 