"Cell" and "tube" are obviously two great keywords with lots of search volume and which can go very well together. So it's not a surprise to see that "celltube" is taken in all major extensions (even though they're all parked pages at this point in time).
The real problem with cell-tube.com is obviously the hyphen (but I'm sure that's why you're actually hesitating to keep it). It does unfortunately kill a large part of its potential value.
Not sure if it would be worth keeping then... But does it get any type-in traffic maybe ?