SyncUp

NOTE: Apple app on https://appstoreconnect.apple.com/ is still waiting for review! This is my first time using Revenue cat and I have been having trouble getting it to work. I am just running out of time(sad face). If you find you have interest in my app, I promise not to put it on any stores until I get it working. I don't dare update the apple app since it is taking so long to review. (Submitted 2/11/2026 3:32 AM). I hope the final connections work for app on google play by the time you get to it. I plan to let people use free version for 2 weeks (336) hours. I have set the configuration for this to be 2 hours. After that, if you try to create a reminder, new group, or personal event, you should get the paywall.

Inspiration It started with a privacy paradox. My 23-year-old daughter mentioned that her friend group’s solution to finding time to hang out was simply sharing their entire calendars with each other. As a developer (and a parent), the idea of granting blanket access to my private schedule just to plan a dinner was a non-starter. I realized there had to be a way to find "common free time" without sacrificing privacy.

However, as I developed SyncUp, I saw the competition announcement and realized that "planning" isn't just about when to meet, but remembering what to do before you get there. This inspired the expansion into a true productivity hybrid. I wanted to build the tool that didn't just put "Radiation Appointment" on the calendar, but intelligently reminded you to "Take medication" 6 hours prior—automatically.

What it does SyncUp is a privacy-first social planner and a powerhouse cross-platform reminder tool.

Socially: It overlays group members' schedules to find free time instantly, without revealing the details of their private events. It includes built-in chat and polling to finalize plans without leaving the app.

Productively: It features a robust reminder engine designed for the multi-device user. If you dismiss a task on your Android phone, it clears from your iPad instantly.

Intelligently: It introduces "Event Templates." If you have a recurring medical appointment (e.g., Radiation), SyncUp automatically schedules the associated tasks (e.g., "Take meds") relative to the appointment time (e.g., "6 hours before"). No more calculating manual reminders for shifting appointment times.

How we built it We chose Flutter to ensure a 60fps, buttery-smooth experience on both iOS and Android—crucial for users who care about aesthetics.

Backend: We utilized Firebase for real-time data syncing. This is the backbone that allows a "Dismiss" action on one device to propagate instantly to another.

Logic: We built a custom recurring-event engine from scratch to handle complex logic that standard libraries often miss, such as "The last Thursday of the month" or "Every 2 weeks on Monday and Wednesday."

Privacy Layer: We engineered a "Blind Sync" algorithm that compares time slots on the server without ever exposing the event titles or details to other group members.

Challenges we ran into The "Natural Language" Trap: We initially wanted users to type "Remind me in 23 minutes." However, we found that parsing natural language often leads to ambiguity and errors. We had to make a hard choice: ship a "guessing" interface, or build a deterministic one. We chose the latter, building a Custom Snooze Dialog that lets users dial in exact times (23 minutes, 4 hours, 2 days) with 100% precision, ensuring the app never sets a reminder for the wrong time.

Cross-Platform Notification Hygiene: One of the biggest annoyances in tech is "ghost notifications"—reminders you've already completed that still clutter your other devices. synchronizing local notification states between Android and iOS required complex logic using cloud functions to silently cancel pending notifications on all devices once a task was marked complete.

Accomplishments that we're proud of The "Relative Reminder" Engine: Successfully building the logic where a Task is linked to an Event's timestamp. If you move the Event, the Reminder moves with it. This is a game-changer for medical adherence and complex itineraries.

Complex Recurrence: We didn't settle for "Daily" or "Weekly." We successfully implemented advanced recurrence (e.g., "The last Friday of the month"), which is a feature often missing even in major productivity apps.

Privacy-Preserving Social: We proved you don't need to share your life story just to find a time to get coffee.

What we learned Context is King: A reminder isn't just a notification; it's a piece of data that lives in a context. A reminder to "Bring Wine" is useless if it pops up at 9 AM; it needs to be linked to the "Dinner Party" event.

The "Ecosystem" Problem: Power users don't stick to one OS. Building for the "switchers" (people who use both Android and iOS) requires a completely different approach to data syncing than building for a single platform.

What's next for SyncUp Natural Language Processing (NLP): While our custom dialogs are precise, we know users love speed. We plan to implement a robust NLP engine to allow users to snooze in a human fashion. I might want to snooze for 23 minutes or snooze until 3:30 this afternoon.

Invite people that don't have the app.

Add a list of task to make your event a success. People in the event can select the task(s) they can do and create a reminder.

Repeating Events. Make managing your regularly scheduled get togethers( Book club, Bunco, Game night.)