Leave your phone in the A3

Hello people ! I play with the idea to buy a cheap mobile phone (e.g.Ebay – Siemens M55, because red lighting etc.) and to put it permanently in my A3-FSE (2th mobile card is no problem) – now I’m just afraid that some bums break the car because of it … or is that not sooo interesting for thieves nowadays !?!? Reason: I get annoyed in and out and constantly charging the battery, although it is almost full – net so bulging … Of course I would put the part in But leave it here in the countryside. Ask for constructive opinions.