(I send a email to Rainer about this.) We use for several years now a mp3 player with little peakers (the speakers are with a little amplifier of 10 watt) I buy it in Holland someware and put the speakers backwards in a small cardboard box and tape it weatherproof with ducktape. The speakers need battery's for the amplifier. I make a lead for a battery pack, same pack as in the boats. I put the mp3 and the batterypack on top and close the lid. Easy to travel and to use!
Now I have seen the same set of speakers (it is an other brand, HAMA) on the site of conrad, they are 25 euro!
Seen at the internet, an original startingmachine for the RC Sailing! The "Startmate" Go to http://westernmodelyachting.com/main.sc You can setup your own startsequence. You have to send the secuence to them and they are willing to arrange it for you.