There is a tool called an iSclack:
http://www.iparts-4u.co.uk/mobile-ph...-iphone-5-ipad
This is a proprietary tool designed for opening specific models of iPhones.

That's all very well, but I wonder if there's a more generic suction tool
for pulling apart two surfaces, and if so what it might be called?
The iSclack has the suction cups in fixed positions with no adjustability,
and has an awkward iPhone holder that's likely to get in the way. If the
surface is fragile there is no way to calibrate the amount of force applied.

I've seen suction cups for glazing and as bodywork dent pullers, which only
provide suction on one surface. Is a tool out there for separating surfaces
by suction, and if so where should I look?

Theo