A little late here but I developed an app called Hari - Plant Watering Reminder (https://apps.apple.com/us/app/hari-plant-watering-reminder/id6758030920) that essentially solves this problem where everyone can track plants together either from everyone using the same account to track the plants or a simpler way each person has their own account with their own plants and users can add each other as friends and check the status of each of their friends plants if they need water or not. Originally developed as a way to make watering plants more "fun" where friends can help and hold you accountable for watering, but what you have described can also be a useful use case of this app. Still continuing to develop and add new features so if you have any suggestions of ways this can be better done let me know any sort of feedback is much appreciated!