I've not done it on a Stilo, so I don't know for definite.... but you're right to ask, as these are CANBUS enabled cars.
The risk you therefore face is that you either get phantom blown bulb warning or a circuit protection error, if it thinks it's drawing too much juice. The best thing to do is check the kit you buy and possibly consult with the retailer / supplier. A lot of the decent kits out there come 'CANBUS safe' now anyway - which typically means they'll have a relay built in already.
If an error does happen it's fairly easy to work around though - you just need a relay. If you have a look on eBay or alike you can pick up relays special made for the job but realistically any 12v relay would probably work if you're keen enough with electronics to know how to wire one up.
Of course you power the relay's switch circuit from the reverse lamp. The switch is insignificant enough to not mess with CANBUS.
Then you connect one side of the relay to a constant 12v supply from somewhere - maybe even battery. Make sure you fuse it as near to the power source as possible!!
The other side of the relay gets connected to 12v input of your parking sensors.
Then when the switch it activated you can have it pass this constant 12v to your parking sensors and hey presto.
