The 2.4 GHz ISM band is one of the most widely used radio bands, and many wireless communication techniques, such as IEEE 802.11, Bluetooth (BT), and ZigBee, use the band. Thus, the interference problem in the band has been an important issue. BT uses BT channel maps which indicate qualities of BT channels to reduce the interference. Fundamentally, the channel map is created after a connection between two BT devices is established, and it is designed to suit BT communications. Viewing the channel map from a new angle, we propose a new scheme which estimates channels' qualities of other standards, not of BT. The proposed scheme named BluS can create the channel map without any BT connection, and estimate channels' qualities of standards using the 2.4 GHz ISM band. We implemented BluS on off-the-shelf smartphones and conducted diverse experiments to verify the performance of BluS. Through the experiments, we confirm that BluS can estimate the channels' qualities accurately and that it is suitable for mobile devices because BluS uses low power.