Remember Napster? The company was notorious in the early noughties, before going legitimate in the latter part of the decade. Since then, it's been preaching the word of online music streaming from computers and the likes of Sonos systems to reasonable effect. Thing is, Spotify has come in and stolen its thunder of late. So what is Napster to do? Take a slice of its mobile market, that's what.At least that's the idea. Napster has gone mobile in the UK for iPhone, iPad, iPod touch and Android devices, offering users of its service access to 15 million tracks. The principle is similar to Spotify – when you happen to be in a 3G or Wi-Fi area, you can search and play any of the tracks in the company's catalogue (which does differ from Spotify), with the option to save albums, tunes or playlists on your mobile device to playback later. Like Spotify, you can sort out playlists online, with an instant sync matching things up on your phone or tablet.Plenty of other things to take in as well, including radio stations, pre-made playlists, the option to 'automix' an artist and save favourite artists for easy access. New releases and current charts are also available, if you want to keep up to date.Napster's 'unlimited' access for computers and connected audio systems is £5 per month, but if you want to go mobile too, you'll be looking at £10 per month. That's the downside really. Spotify has a stranglehold on this kind of thing in the UK and with that in mind, you would have hoped (and expected) Napster to come in a little cheaper to build up some market share. Not so. Which leaves you with a straight choice over which service you prefer. With Spotify still being more social, it might still have a little more to offer.