Reverse geocoding allows you to convert device coordinates into real physical addresses (city, street, building). Currently, flespi supports several geolocation services with dedicated plugins developed to resolve geolocation and add it to a message.
As the accuracy of modern geolocation services is comparable, a decision-making factor in selecting a geolocation service provider is the cost, which is determined by the number of requests over a period of time. With that in mind, here's the list of them being briefly described to assist you in finding the most suitable option for your needs.
Commercial / Pay-as-you-go
Depending on the number of monthly requests, a paid plan starts from $5.00 USD per 1,000 requests. It’s recommended to set daily quota limits on all requests to any API to manage your costs of using the Geolocation API or to meet the demands of your production traffic.
Wialon
Commercial / Free
Proprietary-developed service. Note that if a unit is out of town, you can preset parameters such as 'max distance' from the unit and 'min radius' for address display. It can also detect speeding by comparing the unit's speed with the posted speed limit (eco-driving concept).
Nominatim
Open source / Free
The only one requiring a locally running server. In addition to standard parameters, you can use extratags to request specific features from your Nominatim server (e.g., ‘maxspeed’). Also, it’s up to you to decide which features of OpenStreetMap are important for extensive reporting.
Here
Commercial / Free
Allows you to pick a free plan alongside the paid one for extended features. It can be set up quite flexibly, e.g., you can get the distance in meters from the input geo-coordinates and retrieve various high-level elements.
LocationIQ
Commercial / Free
Basic plan is limited with 5,000 requests per day and 2 requests per second capacity. It offers friendly licensing: use it with or without maps, and get custom plans and SLAs on demand. Moreover, you don't need maps to use the service with flespi plugin.
Gisgraphy
Open source / Paid
Commercial plans start from 30 requests per minute. They may be a good fit for any commercial purposes if you're seeking flexibility, as there are no restrictions: you can store or display results on a map as needed.