I understand the concept of entering data "when at grandma's" but I find that Genealogical information is significantly more complex than a Tweet.
Names, dates, places, source citations, and notes etc would be a real challenge for many of us that do not live with our phone permanently attached to our thumbs :-)
I use the App to allow me to know the who and when information on my ancestors.
If there is a headstone or document with important info I snap a picture. If there is an oral history I can use my voice recorder.
When I get home I can sift through the collected information and enter it as appropriate on my computer using a regular keyboard.