For just over £1, you can get a Kindle download containing the Whole of Shakespeare's output!
Here's the Amazon link.
For £9.99, you can get an iPad app from Faber/Touchpress which offers all of his sonnets, read to you by an 'all-star cast' - including David Tennant, amongst others. This was reviewed in the Sunday Times (24.6.12) - though we can't show you the review online without subscribing to the magazine! Here's the Touchpress link, anyway:- http://www.touchpress.com/titles/shakespeares-sonnets/