The Skopje reminder app whose makers went on to build Letz.

"Feel the superpower of remembering," said MarkO's listing, captured in August 2019 with an address in Skopje, Macedonia. It described a reminder app for smartphones and smartwatches that would nudge you "in the most appropriate time or place," such as the next time you passed a grocery store. Its "AI Recognition" suggested the place, time and people for each reminder, and reminders could be shared over twelve channels, from Facebook and Viber to SMS.

MarkO was a startup of Nino Karas and Martin Anchevski, who had founded the app developer Codewell while still in college; the Play Store address on the listing carries Codewell's name. According to a Boston University profile of Karas, which spells his partner's name Ancevski, MarkO won the Pioneers Festival Community Award in 2014, and in 2015 it "received an investment and joined the acceleration program at Rockstart," the Amsterdam accelerator.

The profile also quotes Karas calling a newer project, Letz, "the next big thing in the personal productivity space." On 30 August 2016, 150sec reported that Letz, an AI chatbot for managing daily tasks co-founded by Karas and Anchevski, had raised a €100,000 seed investment from South Central Ventures, the fund's first in Macedonia. The team had been through Rockstart the year before, it said, and Rockstart had supported the investment in "the new company." By May 2017 Letz, whose assistant was called Lucy, reported more than 30,000 downloads and 8,000 active users, Silicon Canals wrote, and the team was raising a seed round of €700,000 to €800,000. Neither news article mentions MarkO, and no source we found says whether Letz grew out of it.

MarkO's Google Play page now returns not found, marko.rocks shows a parking page for a newly registered domain, and Letz's address, letz.do, no longer resolves.