Speed Camera Detectors are not illegal. Passive detectors which rely on a database of speed camera locations are certainly not illegal and there are no plans to make them illegal. The position with active detectors where the unit itself can detect the proximity of a speed camera is a little less clear. Case law in the UK suggests such units are not illegal although their have been plans to introduce legislation to make them illegal. Active detectors are illegal in some European countries and some States of America.
Some speed camera detectors can operate in both active and passive mode. For passive detectors you will need to ensure you keep an up to date subscription, to ensure that the database is always kept up to date. Micro Fuzion offer free updates on some products.