Is this 100% guaranteed to find the location of a leak or is it just another 'brilliant' idea being sold to you as a way of earning big bucks. I've been doing this job a long time and seen a lot of 'brilliant' ideas come and go.
My advice, wait for a year or two and you'll know if it is really a 'brilliant' idea.
It will only upset you if you sink thousands into it and can't get it back. It is only an investment if it will definitely pay for itself, gain you work and customers and continue to earn its own revenue (aside from your charges).
Can you not hire one for a few occasions and add it to the invoice (maybe make a bit on that) just to see if you will /can, get work for it?
If it becomes a good source of income to you, I would say then is the time to invest your hard earned money into an idea like this.