The tension ometer is handy for high end fussy low spoke wheels like the Lews Or if you have a cracked rim and the maker claims you tightrened to much.
Goes like this:

Mavic: Is that what you say? It's broken?
Chuck: Yeah. That's it, it's broken.
Mavic: You sure?
Chcuk: I'm positive.
Mavic: Maybe you twisted it to hard..
Chuck: I twisted it just right.
Mavic: How could you be so sure?
Chuck: [sighs] You will look in the manual, you will see that this particular model requires a range of 100 to 110 KgF. I routinely twisted the maximum allowable force.
Mavic: How could you be sure you used 110 KgF?
Chuck: Because I used a Park Tool factory certified tensionmeter. The kind used by Dt certified wheel builders. And The Pro road circuit
Mavic: Well, in that case, how can you be sure THAT's accurate?
Chuck: Because a split second before the tensiometer was applied to the spokes , it had been calibrated by top members of Park, the USCF and the UCI... to be dead on balls accurate! Here's the certificate of validation.
Mavic: Dead on balls accurate?
Chuck: It's an industry term.
Mavic: [tosses paper away] I guess the ****ing thing is broken.