The TCS writes in its detailed test report on winter tires 2011:
„"Only the Tiremoni Checkair tm-100 retrofit system can compete with the manufacturer's systems in terms of price/performance. Maintenance costs are low and performance is on par."“
http://issuu.com/touring_online/docs/infotechtcs_winterreifen_2011_de/search
And these low maintenance costs quickly pay for themselves. The sensors can be switched to summer tires; the batteries are simply replaced when the receiver indicates they need replacing. With sensors integrated into the tire, the batteries are sealed in, and when they become depleted, a completely new sensor is required. In that case, a brand new sensor is definitely worthwhile. TireMoni TM 100 – especially with these Christmas offers: http://shop.tiremoni.com