Smartphone volume booster
If you can’t take your swanky speakers along for a pram ride, what you need to do is to make yourself something like this. All you need is a discarded clingfoil roll and lots of tape. Simply slot the phone (you can customise to whatever make of phone you have) in, place it either horizontally or vertically and press play. The best thing is that it’s still palm sized (the stand doubles up as a grip) and NO BATTERIES REQUIRED! Doesn’t give the best audio but does a decent boost (about 80% increase i reckon) and has a nice vintage radio mono aural touch to the ‘output’.