Decent tracker/alarm for a new bike

My recently stolen blade is about to be replaced by a new one. I now quivvering at the thought of chaining it up each day in London in case it get’s stolen again [dont think I could go through that again] - I’ve got the best chain/lock money can buy and I wont be satisfied until it’s chained to something mahoosive each day. On top of this I am looking a tracker but I;ve heard mixed reviews. Can anyone recommend one or are they really not worth the money. I’ve been looking at or a datatool snitcher. Any thoughts?