I've downloaded 3 different apps for my Android (Motorola) phone - they all work to a degree, but all are a pain to use..

I gather there are a couple of good ones for iphones though...

And to be honest I would be more inclined to trust a lightmeter app than a 50 year old Weston meter....once I had used it a few times (and compared the readings to my Minolta Flash V meter..)