I have mentioned this before, but I have used a ESCORT SOLO SD-5110 cordless model for several years now. It has been replaced by different upgraded models threw the years and you can now have their top of the CORDLESS model for around $350.00.
On ebay you can usually get one of the Solo SD-5110 models for around $50.00 and it uses 2 AA batteries that last around a good month before they start to lose their charge, but the detector has a built in sensor that shows you how much power you have at any time. It has served me VERY well with little false alarms and I highly recommend to anyone for the money. You can also get a clip that fits in the unit in place of the suction cups and clip it to the sunvisor on the passenger side. If you do this, there is no cord to show and you cannot see it from the outside!