I like iOS5 reminders app and use it on my iPod touch , however I am looking for an app for OSX lion which provide similar functionality for macOSX in an app which can sync with reminders app for iOS5.
The reminders on your iOS 5 device get synced automatically thorugh iCloud with the reminders in iCal.
I use WunderList (free) on multiple devices iPhone, Macs, Android, Windows, and I share some lists with my friends.
This functionality will be part of OS 10.8 Mountain Lion. Here is the Macworld write up about it.
I did a search in the Apple app store for "Reminders" and and app called "To-do Lists" came up. It looks like what you're looking for.