Your best SOP ideas will never arrive at your desk. Mine show up on buses, in queues, at 1am when sleep is not happening. A mobile app for drafting SOP on the go exists for exactly those moments. Catch the idea or lose it.
I am not going to give you a fake ranked list. Here are five types of apps worth comparing, because different stages need different tools. The distraction-free writer first. You want something that opens fast and gets out of the way. Google Docs is fine here, and its mobile app is genuinely good for drafting. The notes catcher second. Notion shines for this: dump fragments, quotes, half-formed paragraphs into one page per university, shape them later.
Third, the grammar safety net. Grammarly's keyboard catches the errors your tired eyes miss at midnight. It will not fix your structure, but it stops you from submitting "their" when you meant "there." Fourth, the readability checker. The Hemingway approach, short sentences, no fluff, works beautifully on a phone screen, where long paragraphs look terrifying.
Fifth, the review layer. A statement of purpose review app gives your draft a quick clarity pass before a human sees it. Think of it as spellcheck for logic. Run a statement of purpose checker app free tier over the draft while you are at it. Costs nothing, catches the dumb stuff.
My actual setup: capture in Notion, draft in Docs, polish with Grammarly, sanity-check readability, then human feedback. No single SOP editor app on iOS or Android does the whole job. The phone is for capturing. The laptop is for the serious revision.
And when the draft is ready to be shaped around a specific school, the tailoring packs at sopexpert.fyi take it from there.