The "Shabbos App" may "lighten" the issur to a grama on a d'rabbanan of kosev, which would be muttar l'tzorech choleh etc. But not to tell someone why you are late for kiddush. Moreover, it is a nevalah b'reshus haTorah as defined by the Ramban on the mitzvah of Kedoshim Teheyu. As Kedushas Shabbos is an integral halachic and hashkafic component of Shabbos, it is both halachically and hashkafically objectionable.
The comment by the develepor who said "Shabbos will look the way Hashem wants it to look" is absurd. We are responsible for maintaining the spirit of Shabbos. As I noted in an "ancient" Mail Jewish conversation:
From: <YOSEF_BECHHOFER@...> (Yosef Bechhofer) Date: Tue, 2 Nov 93 19:45:46 -0500 Subject: Bicycles on Shabbos and Related Issues I don't wish to comment on the precise Halachic details of bicycles on Shabbos, rather I would like to use this issue to make a related point. There is a "reductionist" tendency in some Halachic circles, albeit not necssarily this one, but others, which is, basically: "If you cannot prove to me what precise definition of pre-established melacha/issur, etc. this fits into, it must automatically be permissible. In this regard it is important to note what the Chazon Ish zt'l says about umbrellas on Shabbos.
In Orach Chaim 52:6 the Chazon Ish takes issue with the conventional wisdom, the Noda b'Yehuda, who bans umbrellas on Shabbos as temporary tents (ohel). Rather, he says, the opening of an umbrella is similar to "fixing" (tikkun mana), but even that is not a true comparison. He goes on to state that the reason one is forbidden to use an umbrella on Shabbos (even where there is an eruv) is because: "It is a very public workaday act (avsha milsa / uvda d'chol) and causes a breach in the sanctity of Shabbos... The determination of which public acts descrate the Shabbos to too great an extent is something that is given over to the sages [of each generation, obviously - there were no umbrellas, much less a prohibition at the time of Chazal] to erect fences in places of possible breaches, and such public matters of Shabbos sanctity are more severe than any private specific prohibitons, because this is a fence for the entire nation for all times. My free translation. I always understood the severity of a Jew's opening his store on Shabbos, despite the relative light nature of the ban on business transactions on Shabbos, as related to the Chazon Ish's fundamental concept.