A lot of these POI collections can be downloaded from websites like Poiplaza.com and
gps-data-team.com. Most of them can easily be converted to the obf format of OsmAnd.
What's more: your TomTom poi files in .ov2 format can directly be converted to osm format by gpsbabel. Then you can use OsmandMapcreator to create your own poi.obf.
Note also that you can use inspector (part of OsmAndCreator) to merge multiple poi files (once in OsmAnd obf format) into one POI obf file.
Finally: Always pay attention to the license on these data files. Are they public domain or proprietary ("real" Tomtom poi files) or only for personal use?
there are ways to upload pois into OSM, also a big bunch at once from OsmAnd if you know your way in sqlite, but always be carefully that you have the right to do so. OSM is all about publicly available and license-free information. Never upload information that is not free from license or from other restrictions.
Harry
On my TomTom I have POI files that include lists of related POIs. For instance, all of the Hannaford grocery stores in the US, or all of the duty free Liquor Outlets in New Hampshire. It would be nice (and quick) to import all of these at once instead of adding them manually to OSMP.