I have been doing this for as long as I can remember.

In Winter time my sports bag is in my garage where it can get colder then in the rest of my house.
So when I arrive at my club , the first thing I do, is get my racket out and put it on the heating system.

Because yes, a cold rubber plays like a brik and is unresponsive. A warmed up rubber above room temperature is a joy to play with.
Personal experience: Don't leave it on there for like an hour or so, 10 minutes is enough to get it above room temperature.

So in Winter it's never a problem for me since there is always some heating on in the club.
And in summer this isn't needed at all.
But this seems like a good way to not be dependent on external heating sources and it will probably give me more control over temperature and heating time.
I could make a routine like 10 minutes before a match to warm it up to a temperature I like the most.

So yes, this thing might be interesting to buy.