A big 3 foot sign attached to your n900 saying...
"If this isn't your personal property....Keep your bloody mitts off"
...
or...
more discreetly....
walk around with a car battery and jumper cables in your carry-on bag and hook them up to your device while not in use...
personally electrified anti-theft...

I let people touch my dog,
my cat,
hell...my "junk" ...
EVER before they touch one of my nxx0's...

I don't care if I hurt their feelings when they say "lemme see that for a sec. .." and I say piss off...
I don't care if they are dying in front of me...
Nobody get's their greasies on my nxx0 for any reason...
I don't ask to see someones personal info, their credit cards, their bank statements, their personal and business contacts, their work,...the list goes on...
asking to play with my daily or work machines is very personal...and very dangerous...in many ways...
so nope...
not happening...

friends want to see cool stuff... I ..myself...personally show them..without letting go of the device for an instant...
or I give them a back-up beater to play with...
Never my own nxx0's...