We recently bought a set of walie-talkies (or 2-way radios!) so that we could communicate when in different places. (For example if I'm doing the outside of a job and Mrs Silly is doing the insides - helps to co-ordinate)
I'd recommend them, very good! They come with a hands-free kit, can be voice activated (with adjustable sensitivity), or used with a little button on the mic.
Also they are normal FM radios, so you can listen to the radio, but if the other person speaks, it breaks in.
Re-chargeable too.
Silly