Best Tiny Bluetooth Bike Speaker 

iVation Bullet Bluetooth Speaker

Want to listen to music from your phone during a bike ride - here is your solution.  The bluetooth speaker pairs perfectly with smart phone and its rechargeable battery lasts up to 4 hours.  It is also packaged with all four colored skins so your can change things up.  All that for only $40. 

Granted, its not the loudest bluetooth speaker - weighing in at one 2W - but its a lot better than the internal speakers in your phone and this can fit in your pocket.  It's the lightest and smallest way to get actual bass tone from your phone.