Children love to mimic what they see mummy and daddy doing, and when it comes to gadgets, they'll absorb the most current devices as if they've been around forever. No doubt you've collected your fair share of old telephones, mobile handsets, computer keyboards, remote controls for broken equipment, maybe even obsolete laptops?! All of these make for great 'accessories' for children to play with and will be highly favoured over play items because these are 'real' and ones that you used to use!
Before handing them over to the children, remove any old batteries just so that they can't leak, but then they're good to be used a play things.
It doesn't matter if an old computer keyboard isn't connected to anything, or that an old mobile phone doesn't have batteries in it and makes no noise. The fact that these are real devices makes them highly attractive to your young children, and being able to play with these items will encourage imaginative play between your little ones.
They can use a computer to do 'work' just like their mummy and daddy do; they can use redundant phone sets to call their friends and family; remote controls will just become gadgets that do something you hadn't even imagined yourself!
Nurturing familiarity with these objects at a young age will make them comfortable with real gadgets when they grow older - they won't be afraid to use phone handsets or computers because they won't be alien to them. Make sure that your children treat these redundant items as they would a working one - make sure they are gentle with them, never throw them, and put them in sensible places rather than leaving them lying in the middle of the floor. Having them treat these items with respect now will also instil that they need to treat real working gadgets with similar care later on.