I use the Headspace app and it doesn't feel nagging at all. No notifications, no remarks when I miss a day. I've tried a few other programs, books and podcasts and Headspace is the only one I've managed to keep using for more than a month (63 days so far). I also really enjoy the narrator, Andy. He gives a lot of helpful advice that has made me stop worrying if I'm "doing it right." A session where I just can't get my mind to rest isn't wasted, it's a learning experience. Maybe it's the app, or maybe it's because this isn't my 1st (or 2nd or 3rd) attempt at building a habit of meditation, but that idea just recently clicked for me and has greatly improved my enjoyment of meditation.

I'll look into the Tara Brach podcast as well though. More opinions never hurt.