Apps similar to Cellular Tower - Signal Finder include Atalaya, which is free and open source. Other options are Tower Collector, Network Cell Info, OpenCellID and Cell Signal Monitor. In total there are seven Network Monitors like Cellular Tower - Signal Finder for Android and the web.
Atalaya is a cell tower monitor which you can get detailed information about the antenna to which your device is connected, such as its identifiers, technology type, bands in use, and the signal quality with the most representative values.
This app collects GPS locations of GSM/UMTS/LTE/CDMA cell towers and sends them to OpenCellID.org database. It is designed to help map the extent of mobile phone network coverage. It is also possible to collect measurements for private purposes and export them to CSV or GPX...
Poland
EU
Real-time cellular and WiFi signal monitoring supports GSM, CDMA, WCDMA, LTE, dual SIMs, with signal plots, band number, interactive maps, route coloring, markers, cellular logs, raw network data, export to KML, MLS, CLF, OpenCellID, and more.
United States
OpenCellID is a collaborative project to create a free worldwide database of Cell IDs and their corresponding location area identity.
Cell Signal Monitor is an advanced network monitor that helps you to watch the state of cellular network by gathering data about cell towers. The app supports GSM, UMTS and LTE networks. There is a Free edition with adds.
Russia
NetMonster collects, shows and stores information about nearby cell towers. Each tower has its unique set of identifiers and NetMonster will show you them.
Crowdsource open collection of mobile towers via app and also visible on the main website https://www.cellmapper.net/map.
Canada
