Sometimes there are situations when a client or a colleague says, "Yes, fine, I will do this tomorrow", and you kind of make an agreement with them. But then a few days pass, and there is no news from them, and nothing is done. Work is not completed.
Obsiously you feel it is necessary to somehow remind them, but there is a typical mistake here. We usually write an awkward message, like "How are you doing with our project?", or even a simpler "How are you doing?". With this exact phrase ("How are you doing?") it is implied that I seem to be interested in how they are doing, but in fact I am reminding them of the task. In this situation, it is better not avoid ambiguous phrases or texting stuff like "Hey, here's a kind reminder". This tone suggests that I believe they have forgotten something. Yet I don't actually know if they have, or not.
It is more appropriate to just copy the description with all materials and details around the task and put at the beginning of the message: "Hi, we're hitting a deadline for this task in # days. The task is still relevant. Here is all the information for your convenience. If there are any questions or problems, or if you do not have enough time, then let me know, and we'll think how to move forward."
This is all that needs to be done to remind about a task.