I have a 2 year old daughter, who has recently (in the past few months) been enjoying the freedom of spending some time playing on her own in the bedrooms with her toys etc. I realise this may be slightly different, however shes only 2, we wont be letting her play outside on her own for obvious reasons. The bedrooms are as safe as can realistically be for her, and we have a baby monitor on downstairs (which she uses as her personal servant bell!) but we are firm believers that she needs this freedom, and will do as she grows older. We wont be cooping her up and restricting her, as is so common these days.

Just be sensible with restrictions, and that's the best route IMO :)