Guinea Fowl make great alarm birds and will let you know if anyone is around, this does include neighbours so they are not suitable for built up areas as they are very loud!
 
They are very hardy birds and naturally will roost high up in the tree's.  In order to prevent the fox taking them it is important to have a large covered run for them with high perches.  They don't like being handled, although you can get them quite tame by bribing them with food.