With all the functionality available in today’s smartphones, it’s easy to forget that their primary purpose is to make, receive, and manage actual phone calls. Luckily, the software on these devices — both the built-in features and the apps we install — make them much more functional as phones in addition to all the extra tricks they can do. Here are five apps that can enhance the “phone” part of your smartphone.

Note: This list is based on an entry in our Smartphones blog.

1: Call Guard

Whether you’re dealing with a “zombie” bill collector who thinks your number belongs to someone on his debtor list, a not-so-secret admirer whose affections you don’t return, or a recurrent wrong number, the ability to block unwanted calls is a big benefit of today’s technology. Many carriers offer this service, but you might have to pay an extra monthly fee for it. Why not install an app to give you the same capability for a small one-time price?

One such app is Call Guard ($2.99 USD), for Android 2.0 and above, which will block both voice calls and SMS text messages from specified numbers. You can create blacklists or you can create whitelists and block all other calls (Figure A).

Figure A

Call Guard

With Call Guard, you can have calls sent to voicemail or use pickup/hangup mode, where the caller doesn’t even get to leave a voicemail message. Another option is to simply set the phone to mute the ringer for specified calls. There’s a lot of flexibility; you can block hidden numbers or all numbers not in your contact list. You can even block SMS messages that contain specified keywords, and you can use filters to block by time of day or day of the week.

2: Call Log Manager Pro

Your smartphone probably provides a call log that shows the history of calls you’ve made and received, but some logs leave a lot to be desired. Call Log Manager Pro ($1.99 USD) can log calls to your calendar, and it lets you group calls not just by the usual types — incoming, outgoing, missed — but also by date, by contact, or according to custom filters you create yourself. You can write your call history to a .CVS or XML file, and you can delete call records by type or for specific contacts. You can even search the log or get graphical analysis information about your calls.

3: Talking Caller ID

When you’re using your phone in the car or another hands-free environment, it helps to be able to hear who’s calling before you answer. Sure, you could just set a custom ringtone for every person in your address book — and if you know only 10 people, that might work fine. Otherwise, you might appreciate an app like Talking Caller ID. It will speak the name or number of the incoming call so you don’t have to look at the phone to find out who’s calling. There’s a free and a paid version ($1.49 USD).

4: Total Recall Call Recorder

It’s often handy to have a full recording of business phone calls so you can go back and verify what was said, either for your own reference or to “prove” what was said if there’s a disagreement about it later. Total Recall Call Recorder ($7.96 USD) lets you record phone calls manually or automatically and you can have it automatically send you or someone else the audio file via email. Unfortunately, on some phones, it won’t record both sides of the conversation (check the list of phones). You should also be aware of the laws regarding the recording of phone calls in your jurisdiction; they vary by location. You can test the free trial before you buy.

5: Google Voice

One of the most useful apps you can get for improving the smartphone calling experience is Google Voice for mobile. It lets you make calls (and send text messages) from your Google Voice number (which can be configured to ring any or all of your phones — mobile, home, work), and it integrates with your Google contacts and your phone’s address book.

One of my favorite features is the ability to get my voicemail messages as email transcriptions. That way, instead of having to play and listen to the message, I can just read the text of it as an email. I have to note, though, that the transcription works better with some voices than others. Some transcripts are almost perfect, but certain accents or dialects can throw it off completely, resulting in gibberish or unintentionally funny results (Figure B). Fortunately, the email with the text transcription also includes an attached .wav file with the audio version of the message, so if you can’t figure it out, you can always listen.

Figure B

Skewed transcription

Google Voice apps are available for Android, BlackBerry, and iPhone; with other phone operating systems, you can use the Web-based version of the service.

Other good options?

What apps do you like best for enhancing the phone capabilities of your smartphone?