What are some alternatives?
When comparing ipstack and Geo IP Tool, you can also consider the following products
ipapi - Web analytics with IP address lookup and location API
ipgeolocation.io - Free IP Geolocation API and Accurate GeoIP Lookup Location Database
IP2Location - IP2Location is a leading provider of IP intelligence service.
IP-API.com - Free IP Geolocation API - lookup any IP address
WIPmania - WIPmania provides a number of free products and services based on WorldIP geolocation database.
whatismyip.cc - External IP Address lookup tool with option to scan the external IP address.