Heating pipes – Heater for a Small Space?

Hi. Does anyone know anything about varmerører such as these or these? I see from the second link that they can be used on boats, but they seem to be the same thing as what are called wardrobe heaters in the UK. In fact, this is exactly what I’m looking for: something to safely install in a small, walk-in(-ish) closet that is completely unheated and often gets very cold.

My questions are: a) Does anyone have any experience with these types of heaters, and do they work well (or not)? b) Are they, in fact, safe? And c) Are they legal for use in enclosed spaces in Norway – or would using one, for example, invalidate my home insurance should anything (perish the though) bad happen (e.g., fire)?

Any info appreciated. Thanks!