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Jpegs are pretty much universal. Almost all drawing and image processing apps will both import and export them.
What kind of editing and tools are you looking for?
I don't have any basic apps that are exactly what you are asking for; but here is what I do have.
Overkill, and then some:
SketchBook Pro: Massive overkill, but it does have line, circle, and square tools. The basic, free, version might be all you need.
Sketch Club: Again, overkill. It also has the basic line, circle, and square tools. There is a social/sharing site, but you don't have to use it.
Both of these involve importing your image into the app, then doing whatever you want. The main problem is that they are so powerful that you'll spend some time learning. Then again, some of the tools might come in handy down the line.
I have several other art/drawing apps, but they don't have the tools you want.
Off to the side a bit:
Skitch: A really basic annotation app, it lets you mark up just about any image and save it back off in most formats. The main advantage is that if you keep the Skitch's files you can go back and edit them. Also works with Evernote; which means you could share a notebook of editable files with other Evernote users. And it's free, so you might as well see if you like it.
If you see a marked up image on this forum, it's probably Skitch. It can be more subtle than most of the images you see, as we tend towards making things obvious here.
Inkpad: This is actually a vector drawing tool, and a nice one. You can import your jpegs from the Photos app and then create vector drawings on top. You can not save as a jpeg, but I'm guessing that Microsoft Paint will be just as happy to import a png; one of the formats averrable. If you've got ideas for migrating your jpeg images to a more flexible, editable vector format, this could be the way to go about it. You could keep the old library updated using png, while simultaneously saving off edited fils as SVG (a standard vector based format). When the majority of the fils have both, then you're ready for a relatively painless transition.
If you decide to do that, I recommend using the imported photo as a guide layer to recreate the image, then discarding it before saving.
I'm sure there are simpler apps available, and probably free. Hopefully someone else can make suggestions. I've always gone for the higher end apps that do more than I want, or very specialized apps that do one or two things very well.
Good luck.