SkyGlass is the hottest, and coolest aircraft tracking software system around. Based on a crowdsourced network of ADS-B receivers, SkyGlass sees more than any other publicly accessible aircraft tracking system. Available for MacOS and Windows.
Available at AviarLabs.com
My always ready go-to earthquake app on my iPhone, and iPad. Multiple feeds from USGS, EMSC, and NRC (Canada). Quickly sort/filter the quake list to meet present need. There's even a historical feed now allowing exploration of quakes over the last ~100 years or so. Quake markers are placed upon your choice of high quality maps, including topo, ocean bathemetry, Open StreetMap, and very nice ESRI satellite imagery. Available at the Apple App Store.
ArcGIS has long been the gold standard for pros in the Geographic Information Systems field. ESRI made a free app, similar to Gooogle Earth, but with far more options. You can change your base maps, add not only kml data layers, but also official GIS data layers available through ESRI's ArcGIS Online subscription platform. But the free version is sooo worth getting! Also worth noting here, if you want to create maps, and other cool stuff, the full ArcGIS Pro app is only $100 for individuals to use for non-commercial purposes!