Ask HN: New Project Recommendations

I'm looking for project suggestions for the new year, something spanning 1-3 months. This is what I'm considering, any suggestions would be appreciated:

1. Automated Stock Trading algorithms (Quantopian or other)

2. Arduino / Pi project (suggestions welcome)

3. Website/app: dating, music, photos, social, finance, etc. Suggestions welcome.

4. Data Analytics project using Machine Learning against a public data source (Astronomy, City Data, etc.)

Please share any experiences with such projects.

Thanks!