It's the Messages app.
And setting reminders based on location is pretty straightforward. Just set a reminder, then tap it and then tap "remind me" - from there you can set a time or location.
Thanks for your kind reply.
now, i have Iphone4, unlocked using Gevey sim. workks gr8.
But, if its the same app with handles iMesses, then how would i know the persone is using iphone with iOS5 ? bocz when i do SMS , it goes on Cell #.
wil it automatically check that this cell # is iphone and with iOS ?
2nd thing, In reminders App, when i set any reminders, and click on Remind ME, i only have one option, "On a Day" if i turn it ON i could select any date and time. But no location option.
thanks