Boxcar [$2.99 + In-App Purchases - iTunes link], a push-enabler for iPhone and iPod touch originally launched with support for a couple of Twitter clients. Then it added a bunch more. As several Twitter clients now offer support for push themselves, what’s Boxcar to do for a 2.0 encore? Add Facebook and Email push, of course, as well as Twitter Search and Twitter Trends.

Okay, sure, some major Twitter clients like Tweetie and Twitterrific still haven’t added push support, so if they’re your go-to apps, Boxcar may still be a go-to middleapp. Likewise, while Google supports Gmail now via GoogleSync, Exchange users can’t hand over their only ActiveSync slot, so email push-enablers still have their place. Lastly — and it’s a big lastly, while Facebook 3.0 for iPhone just launched, it did so without push support, and so if you don’t want to wait for 3.1 to get your push on, well, here’s your middleapp for that as well.

But… it comes with a price. The $2.99 app price comes with one service built in. If you want to add another, like Facebook, you need to make an additional $0.99 in-app purchase. Email, that’s another $0.99. Twitter Trends and Twitter Search likewise. And since you can have multiple Twitter, Email, Twitter Search, etc. set up, you can go from that base $2.99 to $4.99, even $9.99 or more. Basically, you pay for what’s valuable to you. If you’re working customer service and being push-alerted when your company (or your competitor!) and the word “problem” hits Twitter, $0.99 is a steal. If you don’t care about trends or searches, or Facebook for that matter, you get a cheaper entry price for the app.

So, whether this particular app is worth it to you, and whether or not the in-app purchase upgrades are worth it to you, we’re liking options and being able to choose — and pay for — only what we find of value.

So, if you need push now and you decide to try Boxcar 2.0 out, let us know how it works for you, and what you think of the pricing model!

More screen shots after the break…