Here's a decent quality Pedal Wrench which is designed to remove and install 15mm pedals. It has a 26cm long handle, for plenty of leverage, and a comfortable rubber grip. It be used at two different angles, to suit your situation (releasing or tightening). 

Here's a decent quality Pedal Wrench which is designed to remove and install 15mm pedals. It has a 26cm long handle, for plenty of leverage, and a comfortable rubber grip. It be used at two different angles, to suit your situation (releasing or tightening).