yeah, some online tuners are not bad.
but for an actual tuner I have the dogs bollocks of tuners, About £36- £39
but you can get good ones for £10.
Get one that works with the vibrations, they clip onto the guitar and pick up the note thru vibrations. This means people in the same room can still make a noise without interfering wit hthe tuning of the guitar, whereas with the tuners that pick up the sound of the note will also pick up sounds other than the guitar.