Which alarm system to fit?

[RedRag]

Unless you are using the bike every single day, you will def need a trickle charger and a plug in point or you will  also be buying a new battery. They all talk about low drain but this historically does weaken the battery unless it regularly recieved a good charge.
Solar panels charging is a possible option
http://www.maplin.co...-charger-223251

Don't know if it works or not, but for £13 it might be worth a punt!
The lower current one gets good reviews though:

http://www.maplin.co...e-charger-98358