Video Monitoring via web cams

When you say 'play a alarm/audio file' do you mean on your mobile, computer or something else?

From what you've described an outdoor IP web camera should do the job.

An Ip webcam can be set up to send you images and videos as well as emails, and in some cases, SMSs so you can get alerted in a number of ways when motion is detected.

I've got this one: http://www.amazon.co.uk/EyeSpy247Ext-Outdoor-Wireless-I...

But there are loads of IP webcams on the market so you'll need to do some homework on what might work best for you. The only thing I will say is that some of the cheaper cams you'll find are not necessarily best suited so make sure you read up widely on them, otherwise could end up being money down the drain - I say this from personal experience when I was first looking into IP cams and make the classic mistake of buying the 'cheapest'  

FF