I remember reading how someone actually did this. They hired someone from craigslist to sit with them at a coffee shop, quietly watch what they were doing, and poke them to stay on task if they got distracted. It worked out ridiculously well.
I paid someone 10% for this exact service. Nominally, they were supposed to be QA, but they ultimately did very little other than be interested in the project and hound me to make progress. Totally worth it, and to date the only large, multi-year solo project I ever finished and brought to market.