We’re not able to discuss the policy implications around individual existing apps and websites on these public forums for privacy reasons. If you have a concern about the compliance of an existing app with Twitter’s policies, you are free to submit it for review via https://support.twitter.com/forms/platform
Provided that a user has knowingly tagged their Tweet with geo information there is nothing to stop Tweets retrieved via the public Twitter API from being plotted on a map. However, as usual, Tweets should not be stored long-term (it is OK to retain Tweet IDs); take steps to delete or modify Tweets that have been deleted, protected, or modified; Twitter display guidelines and other developer policies should be followed.
If you have specific questions ahead of implementing something yourself, then feel free to share your use case here, or ask for policy support via https://support.twitter.com/forms/platform
